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WorksheetFunction.TDist Method (Excel)

Returns the Percentage Points (probability) for the Student t-distribution where a numeric value (x) is a calculated value of t for which the Percentage Points are to be computed. The t-distribution is used in the hypothesis testing of small sample data sets. Use this function in place of a table of critical values for the t-distribution.

Important note Important

This function has been replaced with one or more new functions that may provide improved accuracy and whose names better reflect their usage. This function is still available for compatibility with earlier versions of Excel. However, if backward compatibility is not required, you should consider using the new functions from now on, because they more accurately describe their functionality.

For more information about the new functions, see the T_Dist_RT, T_Dist, and T_Dist_2T methods.

expression .TDist(Arg1, Arg2, Arg3)

expression A variable that represents a WorksheetFunction object.




Data Type





X - the numeric value at which to evaluate the distribution.




Degrees_freedom - an integer indicating the number of degrees of freedom.




Tails - specifies the number of distribution tails to return. If tails = 1, TDIST returns the one-tailed distribution. If tails = 2, TDIST returns the two-tailed distribution.

Return Value


  • If any argument is nonnumeric, TDIST returns the #VALUE! error value.

  • If degrees_freedom < 1, TDIST returns the #NUM! error value.

  • The degrees_freedom and tails arguments are truncated to integers.

  • If tails is any value other than 1 or 2, TDIST returns the #NUM! error value.

  • If x < 0, then TDIST returns the #NUM! error value.

  • If tails = 1, TDIST is calculated as TDIST = P( X>x ), where X is a random variable that follows the t-distribution. If tails = 2, TDIST is calculated as TDIST = P(|X| > x) = P(X > x or X < -x).

  • Since x < 0 is not allowed, to use TDIST when x < 0, note that TDIST(-x,df,1) = 1 – TDIST(x,df,1) = P(X > -x) and TDIST(-x,df,2) = TDIST(x df,2) = P(|X| > x).