How the calculation works
Monthly growth factor = (1 + nominal annual rate / (100 × frequency))^(frequency / 12). The balance grows by this factor each month, with contributions at the selected time.
Work through an example
Start with 1,000 currency units, contribute nothing, and use 10% nominal annual interest compounded annually for two years. The result is 1,210: 1,000 × 1.1². At 0% interest, adding 100 monthly for those two years gives 3,400 instead.
Assumptions and limitations
The annual rate is nominal and the selected frequency defines its effective growth. Monthly projections interpolate compounding using fractional periods; actual account crediting dates may differ. The rate and inflation stay constant. Taxes, fees, withdrawals, and market volatility are excluded.
The displayed defaults are examples, not live rates. Results are before tax unless explicitly stated. Figures are calculated at full precision, with amounts rounded for display, so adding displayed rows may differ by a small rounding amount.
Questions about this calculator
Is the inflation-adjusted value another account balance?
No. It expresses the final projected balance in today's purchasing power using your constant inflation assumption.
Is this the same rate convention as the SIP calculator?
No. This calculator takes a nominal annual rate and a compounding frequency. SIP takes an effective annual return. The assumptions are displayed on both tools.
Keep the comparison useful
Save one calculation before changing an input. Keep the other assumptions fixed, then compare the result with the saved calculation. For borrowing, look at the total interest and repayment time as well as the scheduled payment. For investing, compare contributions with growth and remember that a constant return is only an illustration.
The table provides the numerical checkpoints behind the chart. Download it as CSV if you want to inspect the values elsewhere. A comparison stays in this tab only and is lost when you reload. No account is needed.
Background reading: Investor.gov: compound interest. Our calculator, worked examples, and explanations are created for SumHatch; the linked organisation does not endorse this tool.
Methodology updated November 10, 2026.