See how your investments could grow. This free investment calculator projects the future value of a lump sum plus regular contributions, showing your total returns, overall ROI, and how much of your ending balance comes from compounding rather than your own money.
Your investment
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Future value
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Enter an amount, return and years
Total invested
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Investment returns
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Total contributions
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Total ROI
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Results update automatically as you type. Estimates only — investment returns vary and are not guaranteed.
Use this free investment calculator to project how much your money could grow. Enter a starting amount, an optional monthly contribution, an expected annual return and a time horizon to see your future value, total returns and overall ROI.
What this investment calculator shows you
An investment calculator projects the future value of an investment using your initial amount, regular contributions, expected annual return and the number of years invested. It shows your ending balance, total invested, investment returns and total ROI — so you can see how much comes from your own money versus compound growth.
It’s built for investing scenarios — stocks, index funds, ETFs or a diversified portfolio — where returns compound over the long term and your time horizon often matters more than the exact rate.
How to use the investment calculator
Enter your initial investment. The lump sum you’re starting with.
Add a monthly contribution (optional). What you’ll invest on a regular basis.
Set your expected annual return. A long-run diversified stock return is often estimated near 7–10% before inflation.
Choose your time horizon in years. Longer horizons dramatically increase compounding.
Read your result. Future value, returns and ROI update instantly.
How investment growth is calculated
Your initial investment grows by compounding, and each contribution compounds from the moment it’s invested. The lump-sum portion follows:
Future value = P × (1 + r ÷ 12)12 × t
Where P is your initial investment, r is the annual return as a decimal, and t is the number of years. Your ROI is the total return divided by the total you invested.
Investment growth example
Suppose you invest $10,000, add $500 a month, and earn an average 8% a year for 20 years:
Detail
Amount
Total invested
$130,000
Investment returns
$213,778
Future value
$343,778
Total ROI
164%
You’d put in $130,000, but compounding more than doubles it — returns of about $214,000 make up the majority of the ending balance.
Why time horizon matters more than timing
The longer you stay invested, the more of your balance comes from growth rather than contributions. The same $10,000 plus $500/month at 8% grows very differently by horizon:
Years invested
Future value
10 years
$113,669
20 years
$343,778
30 years
$854,537
40 years
$1,988,238
Tips for long-term investors
Invest early and stay consistent. Time in the market beats timing the market.
Automate contributions. Regular investing smooths out market ups and downs.
Keep costs low. High fees compound against you over decades.
Diversify. Spreading risk across assets steadies long-term returns.
Reinvest dividends and gains so they keep compounding.
Investment terms glossary
Term
What it means
Principal
The amount you originally invest.
Return
The percentage gain (or loss) on an investment over time.
ROI
Return on investment — total gain divided by the amount invested.
Compounding
Earning returns on both your money and your past returns.
Time horizon
How long you plan to keep the money invested.
Diversification
Spreading money across investments to reduce risk.
Investment Calculator FAQ
How is investment growth calculated?
Your initial investment grows with compounding, and each contribution compounds from the moment it's invested. The lump-sum portion follows Future value = P × (1 + r ÷ 12)12 × t, where P is your starting amount, r is the annual return as a decimal, and t is the number of years.
What is a realistic rate of return to use?
Historically, a diversified stock-market portfolio has returned roughly 7–10% per year before inflation over the long run, though any single year can be much higher or lower. Many people model 6–8% to stay conservative.
What is ROI?
ROI, or return on investment, is your total gain divided by the total amount you invested, expressed as a percentage. A $130,000 total investment that grows to $343,778 has a return of about $213,778, or a 164% ROI.
Does this investment calculator account for inflation and taxes?
No. The projection is shown before inflation, taxes and fees. Your real, after-tax return will be lower, so treat the figure as a pre-tax growth estimate rather than guaranteed spending power.
Is it better to invest a lump sum or contribute monthly?
Both work. A lump sum has more time to compound if invested early, while regular monthly contributions spread your buying across market ups and downs. This calculator lets you combine both.
How does time horizon affect returns?
Dramatically. Because growth compounds, the final decades of a long investment add far more than the early ones. Adding 10 more years often matters more than a slightly higher rate of return.
Is the investment calculator free to use?
Yes, this investment calculator is completely free, needs no sign-up, and gives instant results directly in your browser.
