Investment Calculator
Project the future value of an investment with an initial amount, monthly contributions, rate of return, and compounding.
About the Investment Calculator
Long-term investment growth depends on three levers: how much you start with, how much you add along the way, and the rate of return you earn. This calculator combines all three to project a future value, showing how much of the ending balance came from your own contributions versus market growth.
How It Works
Starting from your initial investment, the calculator compounds the balance at your expected annual return using the compounding frequency you choose, adding your monthly contribution each month. It tracks the running total separately from contributions, so the difference between the final balance and total contributions shows exactly how much growth your money generated.
Balance compounds each period at rate/frequency, with monthly contributions added; Growth = Final Balance − Total Contributions.
Worked example
Scenario: $5,000 to start plus $300 a month for 20 years, at an assumed 8% yearly return compounded monthly.
- The starting $5,000 grows to 5,000 × (1 + 0.08/12)^240 = $24,634.01.
- 240 deposits of $300 grow to 300 × [(1.006667^240 − 1) ÷ 0.006667] = $176,706.12.
- Future value: $24,634.01 + $176,706.12 = $201,340.14.
- Contributions total $77,000, so growth is about $124,340.
Result: A projected $201,340 — about 62% of it from growth rather than contributions.
How to read an investment projection
An investment projection is a scenario, not a forecast. Small changes in assumed return can create large differences over long periods. Compare several return assumptions and remember that taxes, fees, inflation, and market volatility can reduce real-world outcomes.
Tips and common mistakes
- An 8% nominal return is an assumption, not a promise; try 5% and 10% to see a realistic range.
- Fees compound too: a 1% annual fee cuts this example's result by roughly $25,000 over 20 years.
- Results are before tax. Tax-advantaged accounts can keep more of the growth.
Assumptions & Limitations
- Assumes a constant average annual return, which real markets never deliver in a straight line year to year.
- Contributions are assumed to be made every month without interruption.
- Does not model market volatility, sequence-of-returns risk, taxes, or fund fees, all of which affect real outcomes.
- A single average return is a simplification useful for planning, not a guarantee.
Sources and review
Method: Compound growth of the initial amount plus monthly contributions at a constant assumed return, before fees, taxes and inflation.
Sources:
- U.S. Securities and Exchange Commission, Investor.gov guidance on compound interest and investment fees.
Last reviewed: October 2026 by Faheem Ali, founder of CalculatorAnything. The method and examples are provided for transparency; results remain estimates and may contain errors.
Results are estimates for planning and comparison, not financial advice or a lender's quote. Rates, fees, tax rules and regulations vary by country and change over time; confirm figures with your lender or a licensed adviser. Spotted an error? Tell us — see our editorial policy for how corrections are handled.