The Excel TDIST function returns the probability for the Student's t–distribution (right or two–tailed). It is a legacy name — Microsoft now recommends T.DIST.2T and T.DIST.RT.
Syntax
| Argument | Description | |
|---|---|---|
x | Required | The t–value at which to evaluate the distribution. Must be ≥ 0. |
deg_freedom | Required | The degrees of freedom (a positive integer). |
tails | Required | 1 = one-tailed (right) probability; 2 = two-tailed probability. |
How to use it
TDIST gives the area in the tail(s) of the t–distribution beyond x. The tails argument picks one tail (right) or both.
The two-tailed result is exactly twice the one-tailed result. Note that x must be non-negative — TDIST does not accept negative t–values (the modern functions do).
Use the modern names: T.DIST.2T(x, df) replaces the two-tailed form and T.DIST.RT(x, df) replaces the one-tailed (right) form. There is also T.DIST for the left-tail / density.
Try it: interactive demo
Pick a TDIST example to see the formula and its result.
Practice workbook
Frequently asked questions
What modern function replaces TDIST?
T.DIST.2T(x, df) for the two-tailed probability and T.DIST.RT(x, df) for the one-tailed (right) probability. TDIST's tails argument chose between them.Why does TDIST reject negative x?
x ≥ 0 by design. For negative t–values use the symmetric relationship, or switch to the modern T.DIST family, which accepts negatives.How are one-tailed and two-tailed related?
Should I switch to the T.DIST functions?
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