# Sum Function

#### erock24

##### Well-known Member
What sum function would I use to sum from 1 to the specified number. For example, if my number were 5. I would want a formula to sum 1+2+3+4+5 and return 15.

Thanks,

### Excel Facts

How to find 2nd largest value in a column?
MAX finds the largest value. =LARGE(A:A,2) will find the second largest. =SMALL(A:A,3) will find the third smallest
=A1*(A1+1)/2
where A1 is specified number

1+2+3+4+...+n = n(n+1)/2
a + (a+1) + (a+2) + ... + (a+n) = (n+1)(2a+n)/2

a + (a+r) + (a+2r) + (a+3r) + ... + (a+nr) = (n+1)(2a+nr)/2

The sum of an arithmetic series is (number of terms)(first term + last term)/2

What sum function would I use to sum from 1 to the specified number. For example, if my number were 5. I would want a formula to sum 1+2+3+4+5 and return 15.

Thanks,
If your value of interest is in A1, try:

=(A1+1)*A1/2

Edit: A bit slow, but I guess confirms the answers already given. The sum of an arithmetic series is (number of terms)(first term + last term)/2

perfect....thank you.

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