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T-Test Calculator
Run one sample, two sample pooled, Welch and paired t tests with the statistic, degrees of freedom and p value.
Run a t test
t statistic: —
Degrees of freedom: —
Two-tailed p value: —
Group 1 mean: — · SD: — · n:
—
Group 2 mean: — · SD: — · n:
—
How to use the T-Test Calculator
- Paste the values for the first group or sample, separated by commas or spaces.
- Choose the t test type, and enter a hypothesised mean for a one sample test.
- Read the t statistic, degrees of freedom, p value and group means in the results.
Features
- One sample, pooled, Welch and paired t tests
- Two-tailed p value from the Student t distribution
- Group means, standard deviations and counts
- Runs locally, no uploads
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Frequently Asked Questions
Common questions about the free online t-test calculator.
Paste your data, choose the test type and read the t statistic, the degrees of freedom and
the two-tailed p value straight away.
t equals the sample mean minus the hypothesised mean, divided by the standard error, which is
the sample SD over the square root of n.
The pooled test uses t equal to the mean difference divided by the pooled standard error,
with n1 plus n2 minus 2 degrees of freedom.
Welch does not assume equal variances. It keeps the separate variances in the standard error
and uses the Welch formula for degrees of freedom.
The paired test works on the differences between each pair of values, then applies the one
sample formula to those differences.
The p value comes from the Student t distribution, evaluated with a hand-written incomplete
beta function, and is reported as two-tailed.
Use Welch when the groups may have different variances or very different sizes. Pooled is
fine when the two variances are similar.
It measures how many standard errors separate the group means from each other, or the sample
mean from the hypothesised value.
Yes. Paste a column of numbers and the tool splits them on commas, spaces, tabs and new lines
before it calculates.
No. Every calculation runs locally in your browser, so the numbers you paste never leave your
device.
Last updated: October 10, 2026