## About This Tool

The online Sum of Positive Integers Calculator is used to calculate the sum of first n numbers or the sum of consecutive positive integers from n_{1} to n_{2}.

## Sum of Consecutive Positive Integers Formula

The sum of the first n numbers is equal to:

n(n + 1) / 2

The sum of consecutive positive integers from n_{1} to n_{2} is equal to:

n_{1} + (n_{1} + 1) + ... + n_{2} = n_{2}(n_{2} + 1) / 2 - n_{1}(n_{1} - 1) / 2