Reviewed November 2026 · Estimate only, not financial advice.
Two things grow an investment: the money you put in and the returns those returns earn. Enter a starting amount, a monthly contribution and an expected annual return to see the future value — and how much of it is growth, not deposits.
How This Investment Growth Calculator Works
The balance is stepped forward month by month at the monthly return (annual return ÷ 12): each month the balance grows by that rate, then your monthly contribution is added. Contributions are assumed at the end of each month.
FV = P × (1 + r)n + c × ((1 + r)n − 1) ÷ r
P = starting amount, c = monthly contribution, r = monthly return, n = months. Growth = FV − total invested.
Worked example: $10,000 starting amount, $200 a month, 7% expected annual return, 20 years. Total invested = $10,000 + ($200 × 240) = $58,000. Future value = $144,572.72, so growth = $86,572.72 — returns created more than the deposits did.
Practical tips
The return you type is a guess — stress-test it.Run the same plan at 5% and at 9%. The spread between those two outcomes is the real risk of the plan, and it is usually larger than people expect.
Time beats size.Starting ten years earlier usually beats contributing twice as much later. If you can only do a little now, start with a little — the early years compound the longest.
Contributions are the part you control.You cannot control returns, but you can control how much goes in. Raising the monthly contribution by $50 often matters more than chasing an extra 1% of return.
Remember inflation and tax.A 7% nominal return is roughly 4–5% after inflation, and taxable accounts owe tax on gains. Compare this with the Retirement Calculator for after-tax thinking.
Frequently Asked Questions
What return should I assume?
A diversified US stock portfolio has returned about 10% a year before inflation over long periods, and about 7% after inflation. Use 6–7% for a cautious plan and 8–10% for an optimistic one — and always run both.
Are contributions added at the start or end of the month?
At the end of each month. Contributions made at the start of the month would earn slightly more — the difference is small over long horizons.
Does this include dividends?
Yes, in effect: the annual return you enter should be the total return, including dividends reinvested and price growth combined.
How is this different from the compound interest calculator?
The math is the same family. This one is framed for investing — lump sum plus monthly contributions at an expected market return — while the compound interest calculator focuses on savings accounts and compounding frequency.
What about inflation?
This shows the nominal future value. To see purchasing power, divide the result by (1 + inflation)^years, or use the Inflation Calculator.
Is this financial advice?
No. This is a planning estimate only, not financial advice.
