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| Meta Title | Coefficient of Determination (R²) | Calculation & Interpretation |
| Meta Description | The coefficient of determination (R²) is a number between 0 and 1 that measures how well a statistical model predicts an outcome. |
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| Boilerpipe Text | Published on
April 22, 2022
by
Shaun Turney
.
Revised on
June 22, 2023.
The coefficient of determination is a number between 0 and 1 that measures how well a statistical
model
predicts an outcome.
Interpreting the coefficient of determination
Coefficient of determination (
R
2
)
Interpretation
0
The model
does not
predict the outcome.
Between 0 and 1
The model
partially
predicts the outcome.
1
The model
perfectly
predicts the outcome.
The coefficient of determination is often written as
R
2
, which is pronounced as âr squared.â For
simple linear regressions
, a lowercase
r
is usually used instead (
r
2
).
Table of contents
What is the coefficient of determination?
Calculating the coefficient of determination
Interpreting the coefficient of determination
Reporting the coefficient of determination
Practice questions
Other interesting articles
Frequently asked questions about the coefficient of determination
What is the coefficient of determination?
The coefficient of determination (
R
²) measures how well a statistical
model
predicts an outcome. The outcome is represented by the modelâs
dependent variable
.
The lowest possible value of
R
² is 0 and the highest possible value is 1. Put simply, the better a model is at making predictions, the closer its
R
² will be to 1.
Example: Coefficient of determination
Imagine that you perform a simple linear regression that predicts studentsâ exam scores (dependent variable) from their time spent studying (
independent variable
).
If the
R
2
is 0, the linear regression model doesnât allow you to predict exam scores any better than simply estimating that everyone has an
average
exam score.
If the
R
2
is between 0 and 1, the model allows you to partially predict exam scores. The modelâs estimates are not perfect, but theyâre better than simply using the average exam score.
If the
R
2
is 1, the model allows you to perfectly predict anyoneâs exam score.
More technically,
R
2
is a measure of goodness of fit. It is the proportion of
variance
in the dependent variable that is explained by the model.
Graphing your linear regression data usually gives you a good clue as to whether its
R
2
is high or low. For example, the graphs below show two sets of simulated data:
The observations are shown as dots.
The modelâs predictions (the line of best fit) are shown as a black line.
The distance between the observations and their predicted values (the residuals) are shown as purple lines.
You can see in the first dataset that when the
R
2
is high, the observations are
close to the modelâs predictions
. In other words, most points are close to the line of best fit:
Note:
The coefficient of determination is always positive, even when the
correlation
is negative.
In contrast, you can see in the second dataset that when the
R
2
is low, the observations are
far from the modelâs predictions
. In other words, when the
R
2
is low, many points are far from the line of best fit:
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Calculating the coefficient of determination
You can choose between two formulas to calculate the coefficient of determination (
R
²) of a simple linear regression. The first formula is specific to
simple linear regressions
, and the second formula can be used to calculate the
R
² of many types of statistical models.
Formula 1: Using the correlation coefficient
Formula 1:
Â
Â
Where
r
=
Pearson correlation coefficient
Example: Calculating
R
² using the correlation coefficient
You are studying the relationship between heart rate and age in children, and you find that the two variables have a negative Pearson correlation:
Â
Â
This value can be used to calculate the coefficient of determination (
R
²) using Formula 1:
Â
Â
Â
Â
Â
Â
Formula 2: Using the regression outputs
Formula 2:
Â
Â
Where:
RSS = sum of squared residuals
TSS = total sum of squares
Example: Calculating
R
² using regression outputs
As part of performing a simple linear regression that predicts studentsâ exam scores (dependent variable) from their study time (independent variable), you calculate that:
Â
Â
Â
Â
These values can be used to calculate the coefficient of determination (
R
²) using Formula 2:
Â
Â
Â
Â
Â
Â
Â
Â
Interpreting the coefficient of determination
You can interpret the coefficient of determination (
R
²) as the proportion of
variance
in the
dependent variable
that is predicted by the statistical
model
.
Another way of thinking of it is that the
R
² is the proportion of variance that is shared between the independent and dependent variables.
You can also say that the
R
² is the proportion of variance âexplainedâ or âaccounted forâ by the model. The proportion that remains (1 â
R
²) is the variance that is not predicted by the model.
If you prefer, you can write the
R
² as a percentage instead of a proportion. Simply multiply the proportion by 100.
R
² as an effect size
Lastly, you can also interpret the
R
² as an
effect size
: a measure of the strength of the relationship between the dependent and independent variables. Psychologist and statistician Jacob Cohen (1988) suggested the following rules of thumb for
simple linear regressions
:
R²
as an effect size
Minimum coefficient of determination (
R
²) value
Effect size interpretation
.01
Small
.09
Medium
.25
Large
Be careful: the
R
² on its own canât tell you anything about
causation
.
Example: Interpreting
R
²
A simple linear regression that predicts studentsâ exam scores (dependent variable) from their study time (independent variable) has an
R
² of .71. From this
R
² value, we know that:
71% of the variance in studentsâ exam scores is predicted by their study time
29% of the variance in studentâs exam scores is unexplained by the model
The studentsâ study time has a large effect on their exam scores
Studying longer may or may not
cause
an improvement in the studentsâ scores. Although this causal relationship is very plausible, the
R
² alone canât tell us why thereâs a relationship between studentsâ study time and exam scores.
For example, students might find studying less frustrating when they understand the course material well, so they study longer.
Reporting the coefficient of determination
If you decide to include a coefficient of determination (
R
²) in your
research paper
,
dissertation
or
thesis
, you should report it in your
results section
. You can follow these rules if you want to
report statistics in APA Style
:
You should use â
r
²â for statistical models with one independent variable (such as simple linear regressions). Use â
R
²â for statistical models with multiple independent variables.
You donât need to provide a reference or formula since the coefficient of determination is a commonly used statistic.
You should italicize
r
² and
R
² when reporting their values (but donât italicize the ²).
You shouldnât include a leading zero (a zero before the decimal point) since the coefficient of determination canât be greater than one.
You should provide two significant digits after the decimal point.
Very often, the coefficient of determination is provided alongside related statistical results, such as the
F
value
,
degrees of freedom
, and
p
value
.
Example: Reporting
r
² in APA Style
Studentsâ exam scores were predicted by their study time,
r
² = .71,
F
(1,32) = 7.33,
p
= .003.
Practice questions
Other interesting articles
If you want to know more about
statistics
,
methodology
, or
research bias
, make sure to check out some of our other articles with explanations and examples.
Statistics
Chi square test of independence
Statistical power
Descriptive statistics
Degrees of freedom
Pearson correlation
Null hypothesis
Methodology
Double-blind study
Case-control study
Research ethics
Data collection
Hypothesis testing
Structured interviews
Frequently asked questions about the coefficient of determination
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Turney, S.
(2023, June 22).
Coefficient of Determination (R²) | Calculation & Interpretation.
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Retrieved April 2, 2026,
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- [Effect size](https://www.scribbr.com/statistics/effect-size/ "What is Effect Size and Why Does It Matter? (Examples)")
- [Overview of effect sizes](https://www.scribbr.com/statistics/effect-size/ "What is Effect Size and Why Does It Matter? (Examples)")
- [Coefficient of determination](https://www.scribbr.com/statistics/coefficient-of-determination/ "Coefficient of Determination (R²) | Calculation & Interpretation")
- [Model selection](https://www.scribbr.com/statistics/akaike-information-criterion/ "Akaike Information Criterion | When & How to Use It (Example)")
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- [Reporting statistics in APA](https://www.scribbr.com/apa-style/numbers-and-statistics/ "Reporting Statistics in APA Style | Guidelines & Examples")
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# Coefficient of Determination (R²) \| Calculation & Interpretation
Published on April 22, 2022 by [Shaun Turney](https://www.scribbr.com/author/shaunt/ "All articles by Shaun Turney"). Revised on June 22, 2023.
The coefficient of determination is a number between 0 and 1 that measures how well a statistical [model](https://www.scribbr.com/frequently-asked-questions/what-is-a-model/) predicts an outcome.
| Coefficient of determination (*R*2) | Interpretation |
|---|---|
| 0 | The model **does not** predict the outcome. |
| Between 0 and 1 | The model **partially** predicts the outcome. |
| 1 | The model **perfectly** predicts the outcome. |
The coefficient of determination is often written as *R*2, which is pronounced as âr squared.â For [simple linear regressions](https://www.scribbr.com/statistics/simple-linear-regression/), a lowercase *r* is usually used instead (*r*2).
## Table of contents
1. [What is the coefficient of determination?](https://www.scribbr.com/statistics/coefficient-of-determination/#what)
2. [Calculating the coefficient of determination](https://www.scribbr.com/statistics/coefficient-of-determination/#calculating)
3. [Interpreting the coefficient of determination](https://www.scribbr.com/statistics/coefficient-of-determination/#interpreting)
4. [Reporting the coefficient of determination](https://www.scribbr.com/statistics/coefficient-of-determination/#reporting)
5. [Practice questions](https://www.scribbr.com/statistics/coefficient-of-determination/#quiz)
6. [Other interesting articles](https://www.scribbr.com/statistics/coefficient-of-determination/#other)
7. [Frequently asked questions about the coefficient of determination](https://www.scribbr.com/statistics/coefficient-of-determination/#frequently-asked-questions-about-the-coefficient-of-determination)
## What is the coefficient of determination?
The coefficient of determination (*R*²) measures how well a statistical [model](https://www.scribbr.com/frequently-asked-questions/what-is-a-model/) predicts an outcome. The outcome is represented by the modelâs [dependent variable](https://www.scribbr.com/methodology/independent-and-dependent-variables/#dependent).
The lowest possible value of *R*² is 0 and the highest possible value is 1. Put simply, the better a model is at making predictions, the closer its *R*² will be to 1.
Example: Coefficient of determination
Imagine that you perform a simple linear regression that predicts studentsâ exam scores (dependent variable) from their time spent studying ([independent variable](https://www.scribbr.com/methodology/independent-and-dependent-variables/#independent)).
- If the *R*2 is 0, the linear regression model doesnât allow you to predict exam scores any better than simply estimating that everyone has an [average](https://www.scribbr.com/statistics/mean/) exam score.
- If the *R*2 is between 0 and 1, the model allows you to partially predict exam scores. The modelâs estimates are not perfect, but theyâre better than simply using the average exam score.
- If the *R*2 is 1, the model allows you to perfectly predict anyoneâs exam score.
More technically, *R*2 is a measure of goodness of fit. It is the proportion of [variance](https://www.scribbr.com/statistics/variance/) in the dependent variable that is explained by the model.
Graphing your linear regression data usually gives you a good clue as to whether its *R*2 is high or low. For example, the graphs below show two sets of simulated data:
- The observations are shown as dots.
- The modelâs predictions (the line of best fit) are shown as a black line.
- The distance between the observations and their predicted values (the residuals) are shown as purple lines.
You can see in the first dataset that when the *R*2 is high, the observations are close to the modelâs predictions. In other words, most points are close to the line of best fit:

**Note:** The coefficient of determination is always positive, even when the [correlation](https://www.scribbr.com/frequently-asked-questions/what-is-a-correlation/) is negative.
In contrast, you can see in the second dataset that when the *R*2 is low, the observations are far from the modelâs predictions. In other words, when the *R*2 is low, many points are far from the line of best fit:

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## Calculating the coefficient of determination
You can choose between two formulas to calculate the coefficient of determination (*R*²) of a simple linear regression. The first formula is specific to [simple linear regressions](https://www.scribbr.com/statistics/simple-linear-regression/), and the second formula can be used to calculate the *R*² of many types of statistical models.
### Formula 1: Using the correlation coefficient
Formula 1:

Where *r* = [Pearson correlation coefficient](https://www.scribbr.com/statistics/pearson-correlation-coefficient/)
Example: Calculating *R*² using the correlation coefficient
You are studying the relationship between heart rate and age in children, and you find that the two variables have a negative Pearson correlation:

This value can be used to calculate the coefficient of determination (*R*²) using Formula 1:



### Formula 2: Using the regression outputs
Formula 2:

Where:
- RSS = sum of squared residuals
- TSS = total sum of squares
Example: Calculating *R*² using regression outputs
As part of performing a simple linear regression that predicts studentsâ exam scores (dependent variable) from their study time (independent variable), you calculate that:


These values can be used to calculate the coefficient of determination (*R*²) using Formula 2:




## Interpreting the coefficient of determination
You can interpret the coefficient of determination (*R*²) as the proportion of [variance](https://www.scribbr.com/statistics/variance/) in the [dependent variable](https://www.scribbr.com/methodology/independent-and-dependent-variables/#dependent) that is predicted by the statistical [model](https://www.scribbr.com/frequently-asked-questions/what-is-a-model/).
Another way of thinking of it is that the *R*² is the proportion of variance that is shared between the independent and dependent variables.
You can also say that the *R*² is the proportion of variance âexplainedâ or âaccounted forâ by the model. The proportion that remains (1 â *R*²) is the variance that is not predicted by the model.
If you prefer, you can write the *R*² as a percentage instead of a proportion. Simply multiply the proportion by 100.
### *R*² as an effect size
Lastly, you can also interpret the *R*² as an [effect size](https://www.scribbr.com/statistics/effect-size/): a measure of the strength of the relationship between the dependent and independent variables. Psychologist and statistician Jacob Cohen (1988) suggested the following rules of thumb for [simple linear regressions](https://www.scribbr.com/statistics/simple-linear-regression/):
| Minimum coefficient of determination (*R*²) value | Effect size interpretation |
|---|---|
| .01 | Small |
| .09 | Medium |
| .25 | Large |
Be careful: the *R*² on its own canât tell you anything about [causation](https://www.scribbr.com/methodology/correlation-vs-causation/).
Example: Interpreting *R*²
A simple linear regression that predicts studentsâ exam scores (dependent variable) from their study time (independent variable) has an *R*² of .71. From this *R*² value, we know that:
- 71% of the variance in studentsâ exam scores is predicted by their study time
- 29% of the variance in studentâs exam scores is unexplained by the model
- The studentsâ study time has a large effect on their exam scores
Studying longer may or may not [cause](https://www.scribbr.com/methodology/correlation-vs-causation/) an improvement in the studentsâ scores. Although this causal relationship is very plausible, the *R*² alone canât tell us why thereâs a relationship between studentsâ study time and exam scores.
For example, students might find studying less frustrating when they understand the course material well, so they study longer.
## Reporting the coefficient of determination
If you decide to include a coefficient of determination (*R*²) in your [research paper](https://www.scribbr.com/category/research-paper/), [dissertation](https://www.scribbr.com/category/dissertation/) or [thesis](https://www.scribbr.com/dissertation/thesis/), you should report it in your [results section](https://www.scribbr.com/dissertation/results/). You can follow these rules if you want to [report statistics in APA Style](https://www.scribbr.com/apa-style/numbers-and-statistics/):
- You should use â*r*²â for statistical models with one independent variable (such as simple linear regressions). Use â*R*²â for statistical models with multiple independent variables.
- You donât need to provide a reference or formula since the coefficient of determination is a commonly used statistic.
- You should italicize *r*² and *R*² when reporting their values (but donât italicize the ²).
- You shouldnât include a leading zero (a zero before the decimal point) since the coefficient of determination canât be greater than one.
- You should provide two significant digits after the decimal point.
- Very often, the coefficient of determination is provided alongside related statistical results, such as the [*F* value](https://www.scribbr.com/statistics/test-statistic/), [degrees of freedom](https://www.scribbr.com/statistics/degrees-of-freedom/), and [*p* value](https://www.scribbr.com/statistics/p-value/).
Example: Reporting *r*² in APA Style
Studentsâ exam scores were predicted by their study time, *r*² = .71, *F*(1,32) = 7.33, *p* \= .003.
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## Other interesting articles
If you want to know more about [statistics](https://www.scribbr.com/category/statistics/), [methodology](https://www.scribbr.com/category/methodology/), or [research bias](https://www.scribbr.com/faq-category/research-bias/), make sure to check out some of our other articles with explanations and examples.
**Statistics**
- [Chi square test of independence](https://www.scribbr.com/statistics/chi-square-test-of-independence/)
- [Statistical power](https://www.scribbr.com/statistics/statistical-power/)
- [Descriptive statistics](https://www.scribbr.com/statistics/descriptive-statistics/)
- [Degrees of freedom](https://www.scribbr.com/statistics/degrees-of-freedom/)
- [Pearson correlation](https://www.scribbr.com/statistics/pearson-correlation-coefficient/)
- [Null hypothesis](https://www.scribbr.com/statistics/null-and-alternative-hypotheses/)
**Methodology**
- [Double-blind study](https://www.scribbr.com/methodology/double-blind-study/)
- [Case-control study](https://www.scribbr.com/methodology/case-control-study/)
- [Research ethics](https://www.scribbr.com/methodology/research-ethics/)
- [Data collection](https://www.scribbr.com/methodology/data-collection/)
- [Hypothesis testing](https://www.scribbr.com/statistics/hypothesis-testing/)
- [Structured interviews](https://www.scribbr.com/methodology/structured-interview/)
**Research bias**
- [Hawthorne effect](https://www.scribbr.com/research-bias/hawthorne-effect/)
- [Unconscious bias](https://www.scribbr.com/research-bias/unconscious-bias/)
- [Recall bias](https://www.scribbr.com/research-bias/recall-bias/)
- [Halo effect](https://www.scribbr.com/research-bias/halo-effect/)
- [Self-serving bias](https://www.scribbr.com/research-bias/self-serving-bias/)
- [Information bias](https://www.scribbr.com/research-bias/information-bias/)
## Frequently asked questions about the coefficient of determination
[What is the definition of the coefficient of determination (R²)?](https://www.scribbr.com/frequently-asked-questions/definition-of-coefficient-of-determination/)
The [coefficient of determination (R²)](https://www.scribbr.com/statistics/coefficient-of-determination/) is a number between 0 and 1 that measures how well a statistical model predicts an outcome. You can interpret the R² as the proportion of variation in the [dependent variable](https://www.scribbr.com/methodology/independent-and-dependent-variables/) that is predicted by the statistical model.
[What is the formula for the coefficient of determination (R²)?](https://www.scribbr.com/frequently-asked-questions/what-is-the-formula-for-the-coefficient-of-determination-r%C2%B2/)
There are two formulas you can use to calculate the [coefficient of determination (R²)](https://www.scribbr.com/statistics/coefficient-of-determination/) of a [simple linear regression](https://www.scribbr.com/statistics/simple-linear-regression/).
**Formula 1:** 
**Formula 2:** 
[How do I calculate the coefficient of determination (R²) in R?](https://www.scribbr.com/frequently-asked-questions/r%C2%B2-in-r/)
You can use the summary() function to view the [R²](https://www.scribbr.com/statistics/coefficient-of-determination/) of a linear model in R. You will see the âR-squaredâ near the bottom of the output.
[How do I calculate the coefficient of determination (R²) in Excel?](https://www.scribbr.com/frequently-asked-questions/r%C2%B2-in-excel/)
You can use the RSQ() function to calculate [R²](https://www.scribbr.com/statistics/coefficient-of-determination/) in Excel. If your [dependent variable](https://www.scribbr.com/methodology/independent-and-dependent-variables/) is in column A and your independent variable is in column B, then click any blank cell and type âRSQ(A:A,B:B)â.
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> Turney, S. (2023, June 22). Coefficient of Determination (R²) \| Calculation & Interpretation. Scribbr. Retrieved April 2, 2026, from https://www.scribbr.com/statistics/coefficient-of-determination/
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## [Shaun Turney](https://www.scribbr.com/author/shaunt/ "All articles by Shaun Turney")
During his MSc and PhD, Shaun learned how to apply scientific and statistical methods to his research in ecology. Now he loves to teach students how to collect and analyze data for their own theses and research projects.
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## Other students also liked
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| Readable Markdown | Published on April 22, 2022 by [Shaun Turney](https://www.scribbr.com/author/shaunt/ "All articles by Shaun Turney"). Revised on June 22, 2023.
The coefficient of determination is a number between 0 and 1 that measures how well a statistical [model](https://www.scribbr.com/frequently-asked-questions/what-is-a-model/) predicts an outcome.
| Coefficient of determination (*R*2) | Interpretation |
|---|---|
| 0 | The model **does not** predict the outcome. |
| Between 0 and 1 | The model **partially** predicts the outcome. |
| 1 | The model **perfectly** predicts the outcome. |
The coefficient of determination is often written as *R*2, which is pronounced as âr squared.â For [simple linear regressions](https://www.scribbr.com/statistics/simple-linear-regression/), a lowercase *r* is usually used instead (*r*2).
## Table of contents
1. [What is the coefficient of determination?](https://www.scribbr.com/statistics/coefficient-of-determination/#what)
2. [Calculating the coefficient of determination](https://www.scribbr.com/statistics/coefficient-of-determination/#calculating)
3. [Interpreting the coefficient of determination](https://www.scribbr.com/statistics/coefficient-of-determination/#interpreting)
4. [Reporting the coefficient of determination](https://www.scribbr.com/statistics/coefficient-of-determination/#reporting)
5. [Practice questions](https://www.scribbr.com/statistics/coefficient-of-determination/#quiz)
6. [Other interesting articles](https://www.scribbr.com/statistics/coefficient-of-determination/#other)
7. [Frequently asked questions about the coefficient of determination](https://www.scribbr.com/statistics/coefficient-of-determination/#frequently-asked-questions-about-the-coefficient-of-determination)
## What is the coefficient of determination?
The coefficient of determination (*R*²) measures how well a statistical [model](https://www.scribbr.com/frequently-asked-questions/what-is-a-model/) predicts an outcome. The outcome is represented by the modelâs [dependent variable](https://www.scribbr.com/methodology/independent-and-dependent-variables/#dependent).
The lowest possible value of *R*² is 0 and the highest possible value is 1. Put simply, the better a model is at making predictions, the closer its *R*² will be to 1.
Example: Coefficient of determination
Imagine that you perform a simple linear regression that predicts studentsâ exam scores (dependent variable) from their time spent studying ([independent variable](https://www.scribbr.com/methodology/independent-and-dependent-variables/#independent)).
- If the *R*2 is 0, the linear regression model doesnât allow you to predict exam scores any better than simply estimating that everyone has an [average](https://www.scribbr.com/statistics/mean/) exam score.
- If the *R*2 is between 0 and 1, the model allows you to partially predict exam scores. The modelâs estimates are not perfect, but theyâre better than simply using the average exam score.
- If the *R*2 is 1, the model allows you to perfectly predict anyoneâs exam score.
More technically, *R*2 is a measure of goodness of fit. It is the proportion of [variance](https://www.scribbr.com/statistics/variance/) in the dependent variable that is explained by the model.
Graphing your linear regression data usually gives you a good clue as to whether its *R*2 is high or low. For example, the graphs below show two sets of simulated data:
- The observations are shown as dots.
- The modelâs predictions (the line of best fit) are shown as a black line.
- The distance between the observations and their predicted values (the residuals) are shown as purple lines.
You can see in the first dataset that when the *R*2 is high, the observations are close to the modelâs predictions. In other words, most points are close to the line of best fit:

**Note:** The coefficient of determination is always positive, even when the [correlation](https://www.scribbr.com/frequently-asked-questions/what-is-a-correlation/) is negative.
In contrast, you can see in the second dataset that when the *R*2 is low, the observations are far from the modelâs predictions. In other words, when the *R*2 is low, many points are far from the line of best fit:

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## Calculating the coefficient of determination
You can choose between two formulas to calculate the coefficient of determination (*R*²) of a simple linear regression. The first formula is specific to [simple linear regressions](https://www.scribbr.com/statistics/simple-linear-regression/), and the second formula can be used to calculate the *R*² of many types of statistical models.
### Formula 1: Using the correlation coefficient
Formula 1:

Where *r* = [Pearson correlation coefficient](https://www.scribbr.com/statistics/pearson-correlation-coefficient/)
Example: Calculating *R*² using the correlation coefficient
You are studying the relationship between heart rate and age in children, and you find that the two variables have a negative Pearson correlation:

This value can be used to calculate the coefficient of determination (*R*²) using Formula 1:



### Formula 2: Using the regression outputs
Formula 2:

Where:
- RSS = sum of squared residuals
- TSS = total sum of squares
Example: Calculating *R*² using regression outputs
As part of performing a simple linear regression that predicts studentsâ exam scores (dependent variable) from their study time (independent variable), you calculate that:


These values can be used to calculate the coefficient of determination (*R*²) using Formula 2:




## Interpreting the coefficient of determination
You can interpret the coefficient of determination (*R*²) as the proportion of [variance](https://www.scribbr.com/statistics/variance/) in the [dependent variable](https://www.scribbr.com/methodology/independent-and-dependent-variables/#dependent) that is predicted by the statistical [model](https://www.scribbr.com/frequently-asked-questions/what-is-a-model/).
Another way of thinking of it is that the *R*² is the proportion of variance that is shared between the independent and dependent variables.
You can also say that the *R*² is the proportion of variance âexplainedâ or âaccounted forâ by the model. The proportion that remains (1 â *R*²) is the variance that is not predicted by the model.
If you prefer, you can write the *R*² as a percentage instead of a proportion. Simply multiply the proportion by 100.
### *R*² as an effect size
Lastly, you can also interpret the *R*² as an [effect size](https://www.scribbr.com/statistics/effect-size/): a measure of the strength of the relationship between the dependent and independent variables. Psychologist and statistician Jacob Cohen (1988) suggested the following rules of thumb for [simple linear regressions](https://www.scribbr.com/statistics/simple-linear-regression/):
| Minimum coefficient of determination (*R*²) value | Effect size interpretation |
|---|---|
| .01 | Small |
| .09 | Medium |
| .25 | Large |
Be careful: the *R*² on its own canât tell you anything about [causation](https://www.scribbr.com/methodology/correlation-vs-causation/).
Example: Interpreting *R*²
A simple linear regression that predicts studentsâ exam scores (dependent variable) from their study time (independent variable) has an *R*² of .71. From this *R*² value, we know that:
- 71% of the variance in studentsâ exam scores is predicted by their study time
- 29% of the variance in studentâs exam scores is unexplained by the model
- The studentsâ study time has a large effect on their exam scores
Studying longer may or may not [cause](https://www.scribbr.com/methodology/correlation-vs-causation/) an improvement in the studentsâ scores. Although this causal relationship is very plausible, the *R*² alone canât tell us why thereâs a relationship between studentsâ study time and exam scores.
For example, students might find studying less frustrating when they understand the course material well, so they study longer.
## Reporting the coefficient of determination
If you decide to include a coefficient of determination (*R*²) in your [research paper](https://www.scribbr.com/category/research-paper/), [dissertation](https://www.scribbr.com/category/dissertation/) or [thesis](https://www.scribbr.com/dissertation/thesis/), you should report it in your [results section](https://www.scribbr.com/dissertation/results/). You can follow these rules if you want to [report statistics in APA Style](https://www.scribbr.com/apa-style/numbers-and-statistics/):
- You should use â*r*²â for statistical models with one independent variable (such as simple linear regressions). Use â*R*²â for statistical models with multiple independent variables.
- You donât need to provide a reference or formula since the coefficient of determination is a commonly used statistic.
- You should italicize *r*² and *R*² when reporting their values (but donât italicize the ²).
- You shouldnât include a leading zero (a zero before the decimal point) since the coefficient of determination canât be greater than one.
- You should provide two significant digits after the decimal point.
- Very often, the coefficient of determination is provided alongside related statistical results, such as the [*F* value](https://www.scribbr.com/statistics/test-statistic/), [degrees of freedom](https://www.scribbr.com/statistics/degrees-of-freedom/), and [*p* value](https://www.scribbr.com/statistics/p-value/).
Example: Reporting *r*² in APA Style
Studentsâ exam scores were predicted by their study time, *r*² = .71, *F*(1,32) = 7.33, *p* \= .003.
## Practice questions
## Other interesting articles
If you want to know more about [statistics](https://www.scribbr.com/category/statistics/), [methodology](https://www.scribbr.com/category/methodology/), or [research bias](https://www.scribbr.com/faq-category/research-bias/), make sure to check out some of our other articles with explanations and examples.
**Statistics**
- [Chi square test of independence](https://www.scribbr.com/statistics/chi-square-test-of-independence/)
- [Statistical power](https://www.scribbr.com/statistics/statistical-power/)
- [Descriptive statistics](https://www.scribbr.com/statistics/descriptive-statistics/)
- [Degrees of freedom](https://www.scribbr.com/statistics/degrees-of-freedom/)
- [Pearson correlation](https://www.scribbr.com/statistics/pearson-correlation-coefficient/)
- [Null hypothesis](https://www.scribbr.com/statistics/null-and-alternative-hypotheses/)
**Methodology**
- [Double-blind study](https://www.scribbr.com/methodology/double-blind-study/)
- [Case-control study](https://www.scribbr.com/methodology/case-control-study/)
- [Research ethics](https://www.scribbr.com/methodology/research-ethics/)
- [Data collection](https://www.scribbr.com/methodology/data-collection/)
- [Hypothesis testing](https://www.scribbr.com/statistics/hypothesis-testing/)
- [Structured interviews](https://www.scribbr.com/methodology/structured-interview/)
## Frequently asked questions about the coefficient of determination
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