How to use this calculator
Enter your initial investment, annual or monthly contributions, interest rate, and compounding frequency. Optionally add a tax rate on interest income and an inflation rate to see the real purchasing power of your ending balance. Click Calculate to see the full accumulation schedule.
Interest Calculator
Calculate compound interest accumulation with optional contributions, taxes, and inflation adjustment.
About Interest Calculator
About Compound Interest
Compound interest is interest calculated on both the initial principal and the accumulated interest from previous periods. Unlike simple interest, which is calculated only on the principal, compound interest grows exponentially over time — making it a powerful tool for long-term investing.
Compounding frequency matters: the more frequently interest is compounded (daily vs. annually), the higher the effective annual yield. Continuous compounding represents the mathematical limit of this process.
The Rule of 72 is a quick mental shortcut: divide 72 by the annual interest rate to estimate how many years it takes to double your money. For example, at 6% interest, your investment doubles in approximately 12 years (72 ÷ 6 = 12).
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Investment Tips
- →Starting early is more powerful than investing more later — time is your greatest asset.
- →Daily compounding earns slightly more than monthly or annual compounding at the same rate.
- →Even small monthly contributions add up significantly over 20–30 years.
- →Use the inflation rate field to see the real purchasing power of your future balance.
Estimate monthly mortgage payments and amortization.