CalcCompound Interest Calculator
Last updated: 2026-05-09
The Compound Interest Calculator is a free financial calculator. Calculate the growth of an investment with compound interest. Plan your finances accurately and make better economic decisions.
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Common Sizes — Click to Fill
| Principal (€) (€) | Annual interest (%) (%) | Years (años) |
|---|---|---|
| 5000 € | 6 % | 2 años |
| 10000 € | 7 % | 3 años |
| 20000 € | 8 % | 4 años |
| 30000 € | 9 % | 5 años |
| 50000 € | 10 % | 6 años |
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What is compound interest?
Compound interest is the process by which interest earned is added to the principal, and then earns interest itself in the next period. It causes money to grow exponentially over time — not linearly. Albert Einstein reportedly called it "the eighth wonder of the world."
Compound interest formula
Final Amount = P × (1 + r/n)^(n×t)
- P = Initial principal
- r = Annual interest rate (decimal: 5% = 0.05)
- n = Compounding periods per year (annual=1, monthly=12, daily=365)
- t = Time in years
Step-by-step example
Invest $5,000 at 6% annual rate for 10 years, compounded monthly.
- r/n = 0.06/12 = 0.005
- n×t = 12×10 = 120
- Final amount: 5,000 × (1.005)^120 = $9,097
- Interest earned: $9,097 − $5,000 = $4,097 (82% gain)
The power of time
Extend the same example to 30 years: your $5,000 grows to $30,243 — six times your investment. This illustrates why starting to invest early is the most important financial decision you can make.
Compound vs simple interest
- Simple interest: Earns interest only on principal. Linear growth.
- Compound interest: Earns interest on principal plus accumulated interest. Exponential growth.
Related calculators: Loan Calculator · Simple Interest Calculator · Break-Even Point Calculator