Chi-square test calculator
Use goodness-of-fit mode for one categorical variable or independence mode for a contingency table with two categorical variables.
Free statistics calculator
Chi-Square Calculator for Tests, P-Values, and Tables
Use this free chi-square calculator to run a chi-square test online from a test statistic, observed and expected counts, or a contingency table. It calculates the chi-square statistic, degrees of freedom, right-tail p-value, alpha decision, expected counts, and interpretation for goodness-of-fit and independence analysis.
- Chi-square p-value Enter a chi-square statistic and degrees of freedom to calculate the right-tail p-value.
- Goodness-of-fit test Paste observed and expected counts to calculate the chi-square statistic, p-value, and decision.
- Independence test Paste a contingency table to calculate expected counts, degrees of freedom, p-value, and interpretation.
- Homework-ready output Review the method, statistic, degrees of freedom, alpha decision, and short explanation together.
Calculate a Chi-Square Test
Choose the setup that matches your assignment. Use test-statistic mode when you already have a chi-square value and degrees of freedom, goodness-of-fit mode for observed versus expected categories, or independence mode for a contingency table.
Use this mode for a chi-square p-value calculator or a chi-square difference test after you calculate the statistic difference and df difference.
Enter counts separated by commas, spaces, tabs, or new lines.
Leave as 0 unless your course subtracts estimated parameters from degrees of freedom.
Enter observed counts only. Use one row per category and separate columns with commas, spaces, or tabs.
Results
Method
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Chi-Square
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Degrees of Freedom
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P-Value
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Alpha
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Decision
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Interpretation
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Need help interpreting the output? See guidance and tutoring options.
Chi-square goodness-of-fit and independence tests usually use a right-tail p-value. Match the setup, degrees of freedom, and rounding to your course instructions.
Calculation Details
| Item | Value | Contribution |
|---|---|---|
| Calculate a chi-square result to view details. | ||
Need Help Understanding Your Chi-Square Result?
Get help choosing the test, reviewing expected counts, checking assumptions, or explaining the result in context.
- Focused guidance — from $15: review a specific question, output table, or attempted interpretation.
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Mention chi-square in your request and include the test type, what you have tried, relevant counts or anonymized output, and your deadline. For tutoring, add your time zone and preferred times. We confirm the scope, availability, and price before work begins.
Working with SPSS output? Start with our guide to reading SPSS output. For help choosing a test, explore hypothesis testing guidance.
Choosing a Chi-Square Calculator Mode
Choose from three tasks: find a p-value from a chi-square statistic, compare observed and expected category counts, or test association in a contingency table.
Chi-square analysis calculator
The output includes the chi-square statistic, degrees of freedom, p-value, alpha decision, and expected-count details.
Chi-square p-value calculator
Use statistic mode when your software or formula already gives the chi-square value and degrees of freedom.
Chi-square difference test calculator
For nested models, enter the difference in chi-square statistics and the difference in degrees of freedom in statistic mode.
What This Calculator Supports
Chi-square p-value
Enter a chi-square statistic and degrees of freedom to calculate the right-tail p-value.
Goodness-of-fit test
Paste observed and expected counts to calculate the chi-square statistic, p-value, and decision.
Independence test
Paste a contingency table to calculate expected counts, degrees of freedom, p-value, and interpretation.
Homework-ready output
Review the method, statistic, degrees of freedom, alpha decision, and short explanation together.
Chi-Square Formula and Degrees of Freedom
The basic chi-square contribution is (observed - expected)^2 / expected. The calculator adds those contributions across categories or table cells and then uses the matching degrees of freedom.
| Test type | Degrees of freedom | Use when |
|---|---|---|
| Goodness of fit | categories - 1 - estimated parameters | You compare observed counts with expected counts for one categorical variable. |
| Independence | (rows - 1) * (columns - 1) | You test whether two categorical variables are associated. |
| Difference test | df larger model - df smaller model | You compare nested model outputs after calculating the chi-square difference. |
How to Calculate a Chi-Square Test Step by Step
- Choose the correct test: goodness-of-fit, independence, or p-value from statistic.
- Enter observed counts, not percentages.
- Check that expected counts are positive and reasonably large for your course rules.
- Calculate the chi-square statistic and degrees of freedom.
- Use the right-tail p-value and compare it with alpha.
- Write the decision and conclusion in the context of the categories or variables.
Common Mistakes to Avoid
- Using percentages instead of observed counts for a chi-square test.
- Entering expected counts that are zero or negative.
- Forgetting that common chi-square tests use a right-tail p-value.
- Reporting only the p-value without the chi-square statistic, degrees of freedom, alpha, and conclusion.
- Using a standard chi-square calculator for a nested-model chi-square difference test without first calculating the statistic difference and df difference.
Chi-Square Calculator FAQs
What does this chi-square calculator do?
It calculates chi-square p-values from a test statistic, goodness-of-fit results from observed and expected counts, and independence-test results from a contingency table.
Is this a chi-square test online calculator?
Yes. You can calculate a chi-square test online by entering a chi-square statistic, observed and expected counts, or a contingency table.
Why is a chi-square test usually right-tailed?
A larger chi-square statistic means the observed counts are farther from the expected counts, so common chi-square goodness-of-fit and independence tests use the right tail.
How do I calculate a chi-square goodness-of-fit test?
Enter each observed count and the matching expected count. The calculator adds (observed - expected)^2 / expected across categories and uses degrees of freedom equal to categories minus one minus estimated parameters.
How do I calculate a chi-square independence test?
Paste the contingency table of observed counts. The calculator computes expected counts from row totals and column totals, then adds each cell contribution.
What should I report for chi-square analysis?
Report the chi-square statistic, degrees of freedom, p-value, alpha level, decision, and a conclusion in the context of the variables or categories.
Can I use this as a chi-square difference test calculator?
For nested-model comparisons, first calculate the difference between the two chi-square statistics and the difference between their degrees of freedom in your software output. Then use the test-statistic mode with those difference values.
What are expected counts?
Expected counts are the counts predicted under the null hypothesis. In an independence test, they come from row total times column total divided by the grand total.
Related Statistics Help
Use Calculators Responsibly
Use this calculator to check chi-square computations, compare software output, and prepare tutoring questions. For graded work, follow your course rules and explain the method used.