➕ Sum of Arithmetic Series Calculator
Add up the terms of an arithmetic series quickly, without listing and adding every term by hand.
What this calculator finds
An arithmetic series is the sum of the terms of an arithmetic sequence, where each term increases (or decreases) by the same fixed amount. This calculator adds up n terms of such a series without you having to list and total every individual term.
The formula used
The last term is found with a_n = a1 + (n – 1)d. The sum of the first n terms is then S_n = (n/2) × (a1 + a_n), which is equivalent to averaging the first and last term and multiplying by how many terms there are.
This tool is intended for general math learning and educational purposes.
Last reviewed August 2026