Compound Interest Calculator
See how your money grows when interest is earned on both the original amount and the accumulated interest. Add regular contributions and change the compounding frequency to compare scenarios — with a year-by-year growth chart.
Written and reviewed by the CalcBundle editorial team. Transparent formulas · results are estimates, not advice.
Estimated future value
Enter an initial amount or contribution, and a period greater than zero.
What is compound interest?
Compound interest is often called the eighth wonder of finance because it lets your money grow on itself. Each period, interest is added to your balance, and the next period that larger balance earns interest too. The longer the time horizon, the more powerful the effect.
How compounding works
- Future value = P × (1 + r/n)n×t
- P = initial principal, r = annual rate, n = compounding periods per year, t = years
- With recurring contributions, each deposit compounds for the remaining time using the annuity principle.
Simple vs compound interest
Simple interest pays only on the original principal, so $10,000 at 5% earns a flat $500 a year. Compound interest pays on the growing balance, so the same deposit reaches about $16,289 after 10 years of annual compounding — roughly $1,289 more than simple interest.
The effect of contributions
Regular contributions are frequently the biggest lever. Feed the projection into the investment return calculator or the retirement calculator, and compare a one-time deposit with the lump sum investment calculator.
Example
$10,000 at 5% compounded annually for 10 years grows to about $16,288.95 — $6,288.95 of interest. Switch to monthly compounding and it reaches roughly $16,470.
Frequently asked questions
What is compound interest?
Compound interest is interest earned on both your original amount and the interest already accumulated. Over time this compounding accelerates growth compared with simple interest, which is paid only on the original principal.
How does compounding frequency affect growth?
The more often interest compounds — daily rather than annually, for example — the more you earn, because interest starts earning interest sooner. The effect is real but usually smaller than the effect of the rate itself or of adding regular contributions.
How do regular contributions change the result?
Adding a fixed amount each month or year can dramatically increase the final value, because every contribution then compounds for the rest of the period. This calculator shows the value with and without contributions side by side.
Is the projected amount guaranteed?
No. The result is a projection based on the interest rate and contributions you enter. Actual returns vary, especially for investments where the rate is not fixed.
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Disclaimer. This calculator provides estimates for informational purposes only. Results are based on the information you enter and the assumptions used by the calculator. Actual financial, tax, business valuation, lending, marketplace or investment outcomes may differ. Consider consulting a qualified professional for decisions involving significant amounts of money. Results are projections based on the interest rate and contribution assumptions entered. Actual returns may differ.