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📊 T-Test & P-Value Calculator

Compute one-sample and two-sample t-tests from summary statistics. Get t statistics, degrees of freedom, and one-sided and two-sided p-values.

T-Test & P-Value Calculator

Compute one-sample and two-sample t-tests from summary statistics. See the t statistic, degrees of freedom, and one-sided / two-sided p-values.

One-sample t test comparing a sample mean to a hypothesised population mean μ₀.

Sample mean (x̄)

Hypothesised mean (μ₀)

Sample standard deviation (s)

Sample size (n)

t test calculatortwo sample t testp value from t statistic

t statistic

0.745356

Degrees of freedom (df)

P(T ≤ t) (lower-tail)

0.5

P(T ≥ t) (upper-tail)

0.5

Two-sided p-value

Choose whether you are running a one-sample or two-sample t test.
Enter sample means, standard deviations, and sample sizes from your summary statistics.
Read off the t statistic, degrees of freedom, and one-sided or two-sided p-values.

Data are approximately normal in each group, especially important for small samples.
Equal-variance mode assumes both groups share the same population variance.
Welch mode relaxes equal-variance assumptions using an approximate degrees-of-freedom formula.

Which p-value should I report?: For two-sided hypothesis tests (H₀: means are equal), report the two-sided p-value. For one-sided tests, use the lower or upper tail depending on your alternative hypothesis.
When should I use Welch versus equal-variance t tests?: If group standard deviations look different or sample sizes are very unequal, the Welch (unequal variance) test is often preferred. Otherwise, the pooled equal-variance t test is common.
Can I enter raw data directly?: This calculator is built around summary statistics (means, standard deviations, and sample sizes). You can compute those from raw data using the descriptive statistics calculator on ToolHop.

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