How to use this calculator

A finite geometric series adds the first n terms of a geometric sequence.

The method

Sₙ = a₁(1−rⁿ)/(1−r), or n×a₁ when r=1

Enter your values in the labeled fields and choose Calculate. The result panel shows the answer and supporting values when useful.

WORKED EXAMPLE INPUT

First term a₁: 3, Common ratio r: 2, Number of terms n: 8

Select Calculate to evaluate these example values.

Scope and limitations

The r=1 case is handled separately. Very large results may exceed the finite numeric range.

Common questions

Can I use different units?

Use consistent units unless this page is a unit converter. The result follows the units implied by the inputs.

Are results exact?

Displayed values may be rounded. Keep extra precision for important follow-up calculations.

Methods & verification

Formulas use standard mathematical definitions and fixed unit factors where applicable. See our methodology for numerical conventions, rounding, privacy, and limitations.