Student's t Distribution Calculator

Sets the shape of the t distribution — usually the sample size minus one (or minus two, depending on the test).

Small df give heavier tails; with large df the curve is nearly identical to the normal distribution.

The t statistic from your test, e.g. the output of a t-test. The tool reports how likely a value at least this extreme is under the null hypothesis.

The error rate you accept for wrongly rejecting the null hypothesis, as a decimal.

Example: 0.05 is the usual 5% level; the tool returns the matching one- and two-tailed critical t values.