Future Value of an Annuity Calculator

Future value of an annuity is the classic retirement-savings question: if you contribute the same amount every month (or year), and it grows at a given rate, what will you have by a future date? Unlike a single lump-sum future value calculation, this accounts for every contribution compounding for a different length of time. The first contribution grows the longest; the last barely grows at all.

This is the core math behind 401(k) and IRA growth projections, and any "save $X per month" retirement or goal-planning question.

How does this calculator work?

Enter any starting balance you already have, the amount you'll contribute each period, your expected annual rate of return, the number of years, how many contributions occur per year, and whether contributions happen at the start or end of each period.

The calculator grows the starting balance and each contribution forward to the end date and sums them, using the standard future value of an annuity formula.

Each contribution compounds for a different length of time, so the earliest deposits do the heaviest lifting, the same compound growth that powers a single lump-sum future value. This is the engine behind retirement projections; to work backwards from a target instead, the savings goal tool solves for the monthly amount required, and discounting the same stream to today gives its present value.

Worked example

Starting from $0, contributing $500 per month for 20 years at a 7% expected annual return.

Contribution per month

$500

Total contributed over 20 years

$120,000

Future value

$260,463.33

Growth from returns

$140,463.33

How the numbers work

Contributing $500/month for 20 years puts in $120,000 total, but compounding at 7% grows that to $260,463.33, more than double the amount actually contributed, entirely from investment growth.

This is the power of starting early: the earliest contributions have the most time to compound, so a dollar contributed in year 1 is worth far more at the end than a dollar contributed in year 19, even though both are the same $500.

For long time horizons, growth from compounding eventually outweighs your own contributions, which is exactly why starting to save early, even in small amounts, tends to matter more than waiting to save larger amounts later.