Student's t distribution table

A t-table gives the critical value of Student's t for a given number of degrees of freedom and upper-tail area — the multiplier behind every confidence interval on a mean.

How do I read this table?

Each column is an upper-tail area α. For a two-tailed test at the 5% level, read the 0.025 column; for a one-tailed test at 5%, read the 0.05 column. The same numbers serve as confidence-interval multipliers: the 0.025 column is the 95% multiplier.

The values grow as df falls, which is the whole point of the t distribution — a small sample pays for its estimated standard deviation with a wider interval. By df = 1000 the column has all but converged on the z value at the foot of the table.

Every value here is computed from the same functions the app's tests use, so the table cannot disagree with the calculator, which will also handle any value this table does not list.

Other tables