T.INV.2T function
Returns the twotailed inverse of the Student's tdistribution.
Syntax
T.INV.2T(probability,deg_freedom)
The T.INV.2T function syntax has the following arguments:

Probability Required. The probability associated with the Student's tdistribution.

Deg_freedom Required. The number of degrees of freedom with which to characterize the distribution.
Remarks

If either argument is nonnumeric, T.INV.2T returns the #VALUE! error value.

If probability <= 0 or if probability > 1, T.INV.2T returns the #NUM! error value.

If deg_freedom is not an integer, it is truncated.

If deg_freedom < 1, T.INV.2T returns the #NUM! error value.

T.INV.2T returns that value t, such that P(X > t) = probability where X is a random variable that follows the tdistribution and P(X > t) = P(X < t or X > t).

A onetailed tvalue can be returned by replacing probability with 2*probability. For a probability of 0.05 and degrees of freedom of 10, the twotailed value is calculated with T.INV.2T(0.05,10), which returns 2.28139. The onetailed value for the same probability and degrees of freedom can be calculated with T.INV.2T(2*0.05,10), which returns 1.812462.
Given a value for probability, T.INV.2T seeks that value x such that T.DIST.2T(x, deg_freedom, 2) = probability. Thus, precision of T.INV.2T depends on precision of T.DIST.2T.
Example
Copy the example data in the following table, and paste it in cell A1 of a new Excel worksheet. For formulas to show results, select them, press F2, and then press Enter. If you need to, you can adjust the column widths to see all the data.
Data 
Description 

0.546449 
Probability associated with the twotailed Student's tdistribution 

60 
Degrees of freedom 

Formula 
Description (Result) 
Result 
=T.INV.2T(A2,A3) 
Tvalue of the Student's tdistribution for the terms above (0.606533076) 
0.606533 