Investment Calculator
Estimate how your investments could grow with an initial deposit, monthly contributions, and a return rate.
Results
Future Value
$300,851
Total Contributions
$130,000
Investment Growth
$170,851
Starting Amount
$10,000
Growth Multiple
2.31x
Assumes a fixed annual return compounded monthly. Actual investment returns vary and are not guaranteed.
How This Investment Calculator Works
This investment calculator projects the future value of your portfolio by combining two sources of growth: your initial lump sum and your ongoing monthly contributions, both compounded monthly at your chosen annual return rate. It is the same math used by retirement planners and brokerages to illustrate long-term growth, simplified to four inputs so you can quickly test different scenarios.
The annual return rate you choose matters enormously. Historically, a diversified U.S. stock portfolio has returned around 7% per year after inflation over long periods, while bonds have returned closer to 2-3%. A balanced portfolio of stocks and bonds often lands somewhere in between. Try running the calculator at 5%, 7%, and 9% to see how sensitive your results are to the assumed rate, especially over longer time horizons.
Consistent monthly contributions are often more impactful than the size of your initial investment, especially for younger investors. Someone who invests $500 a month for 30 years at 7% contributes $180,000 of their own money but ends up with over $610,000, more than triple their contributions thanks to compounding.
Remember that this calculator assumes a constant rate of return, but real markets are volatile and move up and down year to year. Use these projections as a long-term planning estimate, not a guarantee, and revisit your numbers periodically as your income, goals, and market conditions change.
Frequently Asked Questions
What rate of return should I use?
A common assumption for a diversified stock portfolio is 7% per year after inflation, based on long-run historical U.S. stock market averages. If your portfolio includes bonds or cash, a lower rate such as 4-6% may be more realistic. It's wise to run the calculator with a range of rates to see how your results change.
How do monthly contributions affect my final balance?
Monthly contributions compound just like your initial investment. Each deposit has time to grow, so earlier contributions have a bigger impact than later ones. Increasing your monthly contribution even modestly, especially early on, can substantially increase your future balance over a long time horizon.
Does this calculator account for taxes or fees?
No. This calculator shows gross investment growth before taxes, account fees, or fund expense ratios. Taxable accounts may owe capital gains tax on withdrawals, and fund fees can reduce your effective return by a fraction of a percent each year. For tax-advantaged accounts like a 401(k) or IRA, the numbers shown are closer to what you'd actually keep.
What is the difference between an investment calculator and a compound interest calculator?
A compound interest calculator typically projects growth of a single lump sum with no further deposits. This investment calculator adds recurring monthly contributions on top of an initial amount, which better reflects how most people actually invest, for example through automatic contributions to a brokerage or retirement account.