Chi-Square Critical Value & P-Value Calculator
Use this tool like a digital chi-square table: enter degrees of freedom and significance level to find critical values instantly. If you also provide a chi-square test statistic, the calculator returns p-values and a reject/do-not-reject decision.
Leave the statistic blank if you only need table critical values.
What is a chi-square table calculator?
A chi-square table calculator is a faster alternative to looking up printed chi-square distribution tables. In hypothesis testing, you often need a critical value based on two inputs:
- Degrees of freedom (df)
- Significance level (α), such as 0.10, 0.05, or 0.01
Instead of scanning rows and columns manually, this tool computes the exact critical value and can also estimate p-values when you provide your test statistic.
How to use this chi-square calculator
Step 1: Enter degrees of freedom
Degrees of freedom depend on your test setup. For common tests:
- Goodness-of-fit test: df = categories − 1 − estimated parameters
- Independence/homogeneity test: df = (rows − 1)(columns − 1)
- Variance test: df = n − 1
Step 2: Choose alpha and tail type
Most chi-square tests in practice are right-tailed, but variance testing may involve a two-tailed setup. This calculator supports right, left, and two-tailed critical values.
Step 3: Optional statistic input
If you already calculated a chi-square test statistic, enter it to get p-values and an immediate hypothesis decision.
Interpreting results
After calculation, you will see:
- The relevant critical value(s)
- The rejection rule for your chosen tail
- Optional p-values (right, left, and two-tailed) when a statistic is entered
For right-tailed tests, reject the null hypothesis when your statistic is greater than or equal to the critical value.
Quick example
Suppose df = 10 and α = 0.05 for a right-tailed test. The calculator returns a critical value near 18.307. If your computed chi-square statistic is 20.1, then 20.1 > 18.307, so you reject the null hypothesis at the 5% level.
Why this is better than static chi-square tables
- Handles non-standard alpha values (not just 0.10, 0.05, 0.01)
- No interpolation needed
- Provides p-values directly
- Generates a mini row of common right-tail critical values for your df
Common mistakes to avoid
- Using the wrong degrees of freedom formula
- Confusing right-tailed and left-tailed setups
- Comparing a statistic to the wrong critical region in two-tailed tests
- Rounding too early during manual calculations
Final notes
This chi-square table calculator is designed for fast, practical statistics work. It is ideal for students, analysts, and researchers who need critical values and p-values without searching through large statistical tables.