Arithmetic Sequence Calculator

About this calculator

This calculator finds the nth term of an arithmetic sequence using aₙ = a₁ + (n−1)d, and the sum of its first n terms using Sₙ = n/2·(a₁ + aₙ), where a₁ is the first term and d is the common difference added at each step. These closed-form formulas let you jump straight to any term or partial sum without manually adding up a long list of numbers one at a time.

Algebra and pre-calculus students working through sequences-and-series homework, teachers building practice problems, and anyone modeling a linearly growing or shrinking pattern — such as stadium seating rows, savings that increase by a fixed amount each month, or a step-loaded staircase — uses this. Enter the first term, common difference, and n to get the nth term and the running sum.