T.DIST.2T Function

Excel Functions › Statistical

Excel 2010+ Statistical

The Excel T.DIST.2T function returns the two-tailed Student's t-distribution — the combined probability in both tails for a given t-value and degrees of freedom.

Quick answer:
=T.DIST.2T(2,10) two-tailed probability ≈ 0.0734

Syntax

=T.DIST.2T(x, deg_freedom)
ArgumentDescription
xRequiredThe t-value at which to evaluate the distribution. Must be non-negative.
deg_freedomRequiredThe degrees of freedom (a positive integer).

How to use it

T.DIST.2T sums the area in both tails beyond ±x — exactly the two-sided p-value you report when testing whether a t-statistic differs from zero in either direction.

=T.DIST.2T(2, 10) // both tails ≈ 0.0734

Because it counts both tails, T.DIST.2T(x, df) equals exactly twice T.DIST.RT(x, df). The x argument must be zero or positive; a negative value returns an error.

=2*T.DIST.RT(2, 10) // same ≈ 0.0734

Two-tailed vs one-tailed: use T.DIST.2T when your hypothesis is “different from” (either direction) and T.DIST.RT when it is directional (“greater than”). The two-tailed p-value is always the larger of the two.

Try it: interactive demo

Live demo

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Result:

Practice workbook

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Frequently asked questions

What is a two-tailed probability?
It is the combined area in both tails of the distribution — beyond +x and below −x. It answers “how likely is a t-value at least this far from zero in either direction?”
How does T.DIST.2T relate to T.DIST.RT?
By symmetry, T.DIST.2T(x, df) is exactly 2 × T.DIST.RT(x, df). The two-tailed value is simply double the right tail.
Can x be negative?
No — T.DIST.2T requires a non-negative x and returns an error for negative values. Because the distribution is symmetric, take the absolute value of your t-statistic first.
When should I use the two-tailed version?
Use it for a non-directional hypothesis (“the means are different”). For a directional test (“greater than” or “less than”) use the one-tailed T.DIST.RT instead.

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Related functions: T.DIST · T.DIST.RT · T.INV.2T · T.INV · T.TEST · NORM.DIST