Excel, how to find column number of min value?

Solution 1:

Assuming your data is in columns A to D, the following formula in E will return the relative numeric index of the smallest value (with 1 = 1st column = A, 2 = 2nd column = B, etc.) for row 1:

=MATCH(MIN(A1:D1),A1:D1,0)

Explanation: the MATCH() function returns a relative index for a cell value in a cell range, and the nested MIN() for the same range provides the value to check for.