Investment Calculator
Project investment growth and compare your contributions with estimated gains.
Educational estimate only. This is not financial, investment, tax, legal or lending advice, a quote or a guarantee. Read the disclaimer.
Your inputs
Illustrative growth by year.
How this calculator works
P is the starting balance, C is the contribution at each month-end, r is the entered annual percentage divided by 100 and then 12, and n is years × 12. The rate is treated as a nominal annual rate, not APY or an effective annual return. Returns are constant in this illustration; no taxes, fees, inflation, withdrawals or market volatility are modeled. Fractional years use fractional exponents; the chart shows completed years only. Total return shown is (FV − total contributed) ÷ total contributed × 100, or not applicable if nothing was contributed. It is a cumulative gain relative to contributions, not annualized, time-weighted or money-weighted performance. Investment losses are possible.
Dollar results are in USD and generally rounded to the nearest whole dollar; salary equivalents and percentage outputs use two decimal places. Calculations retain JavaScript floating-point precision between steps rather than rounding every payment to cents. Displayed components may not sum exactly to displayed totals. Payoff times use whole monthly payment periods. Defaults are examples, not current rates or recommendations.
Full methodology · About the publisher and corrections
Content and calculation checks: October 12, 2026. Educational estimates; no independent professional certification is claimed.
Worked example: $10,000 plus $500 per month
Starting with $10,000 and adding $500 per month for 20 years at an illustrative 7% annual return produces about $300,851 in this model. Total contributions are $130,000, with about $170,851 of modeled growth.
The displayed cumulative gain is about 131.42% relative to contributions. This is not an annualized performance figure and does not account for taxes, fees or market volatility.
Practical guide
Stress-test an investment projection
- Run conservative, middle and optimistic return assumptions.
- Compare a larger contribution with a longer time horizon; time can have a substantial compounding effect.
- Do not treat a constant return as an expected year-by-year path.
- For retirement-specific accumulation, compare the Retirement Calculator and 401(k) Calculator.
How to use the result
Change one assumption at a time to compare scenarios. For example, test a lower rate, larger contribution, different term or extra payment. This makes the calculator most useful as a decision-support tool rather than a single-number answer.
Important financial decisions can depend on taxes, fees, eligibility rules, lender policies, market returns and personal circumstances that this simplified calculator does not capture.
Frequently asked questions
Is this investment calculator free?
Yes. SumStride calculators are free to use and do not require an account.
Are the results exact?
No. Results are estimates based on the values you enter and the assumptions described on this page. Real-world fees, taxes, rates, policies and timing can differ.
Does SumStride save my inputs?
No account is required. The calculator runs in your browser; SumStride does not need your entered values to perform the calculation.