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Returns & Compounding Calculators
Calculate how much your principal and monthly contributions grow with compounding, and how much you need each month to reach a target amount.
Enter 0 to skip the real-value calculation.
Enter your values and press Calculate
Projected amount after 20 years
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Total principal contributed
Investment gain
Return
How to use
Choose whether to see the future value, or to work backwards to how much you need each month to reach a target amount.
Enter your initial investment, monthly contribution, expected annual return and period. For long-term stock returns, 5-8% is a commonly used conservative range.
See how principal and gains diverge year by year, and share the result with a link.
Principal grows using the period return, which is the annual return r divided by the compounding frequency n, and the contribution is added at the end of each month. When the monthly contribution and the compounding frequency differ, the calculation uses the effective monthly return (1 + r/n)^(n/12) − 1.
(1 + r/n)^(n/12) − 1
Real value is the future amount discounted by the inflation rate, showing how much purchasing power it has in today's money.
Starting balance $0, monthly compounding, no inflation adjustment. Each deposit is made at the end of the month.
These are the results the calculator returns for the same inputs. The rates are assumptions, not forecasts.
The calculator converts the annual return to an effective monthly rate, (1 + r/n)^(n/12) − 1, and applies the future-value formula for monthly deposits. It is plain math with no tax law or reference date; the assumptions you enter (return, period, compounding) decide the result. Taxes and fees are not included.
Even at the same 7% a year, monthly compounding gives an effective annual return of about 7.23%. The longer the period, the bigger the gap, but in stock investing the 'expected annual return' is itself an estimate, so taking a conservative view with annual compounding is also an option.
Compare scenarios: the current rate for deposits, about 4-5% for a bond-stock mix, and about 5-8% for long-term stock index investing. If you want to see actual historical data, use the DCA Calculator.
This calculator is pre-tax. You can see tax differences by account type in the After-tax Return Comparison by Account tool.
The amount your initial investment grows to over the period is subtracted from the target, and the monthly contribution needed to fill the remainder is solved with the annuity formula.
Results are estimates based on your inputs and simplified assumptions, and are for reference only, not a basis for investment decisions.
Last updated: November 2, 2026
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