Chi-Square Test Calculator
Goodness-of-fit test from observed and expected counts.
Enter your values
ⓘ Live results
Results
- Chi-square
- 38.1818
- p-value
- < 0.0001
- Verdict
- p < 0.001 — very strong evidence
- Degrees of freedom
- 5
- Biggest contributor
- Category 5 (17.45)
- Cramér's V
- 0.195
Quick answer
Chi-square sums (observed − expected)² ÷ expected across categories; large values mean the observed pattern is unlikely under the expected model.
χ² = Σ (O − E)² ÷ E
How to use the Chi-Square Test Calculator
- 1Enter the counts you actually observed, in category order.
- 2Enter the counts the null hypothesis expects — equal shares if you have no other model.
- 3Check the p-value, then look at which category contributed most to the total.
Worked example
Using the values the calculator loads with:
Inputs
- Observed counts30, 14, 34, 45, 57, 20
- Expected counts33, 33, 33, 33, 33, 33
Results
- Chi-square38.1818
- p-value< 0.0001
- Verdictp < 0.001 — very strong evidence
- Degrees of freedom5
- Biggest contributorCategory 5 (17.45)
- Cramér's V0.195
Frequently asked questions
What if an expected count is below 5?
The chi-square approximation gets unreliable. Combine small categories or use Fisher's exact test.
Can I use percentages?
No. Chi-square must run on raw counts; percentages throw away the sample size the test depends on.
About this calculator
- Built and reviewed by James Whitfield · How we build and test calculators
- Report an error
Results are estimates for general information. For medical, legal, structural or financial decisions, confirm with a qualified professional.