Compound Interest Calculator
Compound interest calculator that grows any principal with reinvested interest. Enter the starting amount, the annual interest rate, the number of years and choose how often interest compounds — annually, semi-annually, quarterly, monthly or daily — and instantly see the final value, the total interest earned and the doubling time. The calculator uses the standard compound interest formula F = P(1+r/k)^(n·k) and shows a year-by-year table so you can watch the balance accelerate, plus the famous Rule of 72 estimate. Whether you are planning investments, retirement savings, education funds or long-term wealth, seeing compounding on paper makes the power of time tangible. All calculations run locally in your browser with no registration, no upload and no privacy risk; the bilingual interface, responsive layout and one-click PNG download make it a clean, elegant and free tool for students, investors, families and anyone curious about how money grows. Fast and accurate, top rated 2024 2025, SEO optimized long tail keywords.
Compound Interest Calculator
| Year | Interest this year | Year-end balance |
|---|---|---|
| 1 | 600.00 | 10,600.00 |
| 2 | 636.00 | 11,236.00 |
| 3 | 674.16 | 11,910.16 |
| 4 | 714.61 | 12,624.77 |
| 5 | 757.49 | 13,382.26 |
| 6 | 802.94 | 14,185.19 |
| 7 | 851.11 | 15,036.30 |
| 8 | 902.18 | 15,938.48 |
| 9 | 956.31 | 16,894.79 |
| 10 | 1,013.69 | 17,908.48 |
What is it
Compound interest is interest earned on interest. Instead of paying you only on the original principal, each period's interest is added to the balance, so the next period earns on a bigger base. The formula F = P(1+r/k)^(n·k) captures this: P is the principal, r the annual rate, k the number of compounding periods per year and n the years. The more often interest compounds, the faster money grows.
Notes & fun facts
Legend says Albert Einstein called compound interest the eighth wonder of the world: "He who understands it, earns it; he who doesn't, pays it." Whether or not he said it, the rule of 72 makes the idea concrete — divide 72 by the annual rate and you get roughly the years needed to double your money.
Origin & history
The mathematics of compounding dates to the 17th century, when Jacob Bernoulli studied continuously compounded interest and discovered the constant e. The Rule of 72 itself appears in Luca Pacioli's 1494 book Summa de arithmetica, making it over 500 years old.
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