=A1*(A1+1)/2

Sum of digits 1 to n =n(n+1)/2

HTH

"bj" wrote:

try
=IF(MOD(A1,2)=0,(A1+1)*(A1/2),(A1*((A1-1)/2)+A1))
if you want 6 = 21 and 6 is in A1

From what you asked (Sum of numbers less than the input number)
=if(MOD(A1,2)=1,A1*(A1-1)/2,(A1-1)*(A1-2)/2+A1-1)
if you really wanted 6=15

"Scott" wrote:

If I want to be able to input a number in a cell and in another cell take the
sum of the number with all of the numbers smaller than it without a macro how
would I do it?

Example:
If I put a 6 in a cell, I want another cell to output 21 (6+5+4+3+2+1)

Thanks!