Future Value Calculator
See what a lump sum plus monthly contributions grows to at any rate of return.
Try an example
$144,572.72
About this calculator
How This Future Value Calculator Works
Enter a present amount, a monthly contribution, an annual interest rate, and a number of years, and the calculator projects what the total grows to — combining growth on your initial deposit with growth on every contribution added along the way.
Worked Example
Starting with $10,000, adding $200 every month, at 7% annual interest (compounded monthly) for 20 years grows to $144,572.72. You'll have contributed $58,000 of your own money in total — the remaining $86,572.72 is interest.
The Formula
Future value combines two pieces: the lump sum growing on its own, P(1 + r)ⁿ, plus the contributions growing as they're added, C × [(1 + r)ⁿ − 1] ÷ r — where P is the present amount, C is the monthly contribution, r is the monthly interest rate (annual rate ÷ 12), and n is the number of months. Adding these together gives the total future value.
Why Starting Early Matters More Than Contributing More
Because interest compounds on interest, money that's been growing longer contributes disproportionately to the final total — a dollar invested in year one has decades to compound, while a dollar invested in the final year barely grows at all. This is why the same total contributed can produce very different results depending on when it was added, and why starting early — even with smaller amounts — often outperforms starting later with larger ones.
For a single lump sum with no ongoing contributions, the Compound Interest Calculator is a more direct fit.
Worked example
A $10,000 head start plus $200/month for 20 years at a 7% annual return grows to about $144,585 — $58,000 of that is what you put in; the rest, about $86,585, is investment growth.
Frequently asked questions
What's the formula behind this?
It combines two compound-growth calculations: the starting amount compounded monthly at your rate, plus the future value of a monthly contribution series (an ordinary annuity) at the same rate.
Why does starting early matter so much?
Growth compounds on growth — money invested for 30 years earns returns on returns for three decades, while the same money invested for 10 years only gets a third as long to compound, even at the same rate.
Is a 7% return realistic?
It's a common simplified estimate for long-run stock market average returns before inflation, but actual returns vary year to year and aren't guaranteed — use a rate that matches your own investments and risk tolerance.
Does this account for taxes or fees?
No — this is a pure compound-growth calculation. Taxes, fund fees, and account type (like a Roth vs. traditional IRA) all affect what you actually keep, and aren't factored in here.