Interest Calculator
Free interest calculator. Calculate simple and compound interest — enter your principal, rate, and time to see final balance, total interest earned, and a year-by-year breakdown.
Summary
Year-by-year breakdown
| Year | Balance | Interest earned | Total interest |
|---|
Free Online Interest Calculator
Whether you're saving for retirement, planning an investment, or just curious how your money grows over time, our interest calculator gives you a clear picture instantly. Enter your principal, rate, time period, and compounding frequency to see your final balance, total interest earned, and a full year-by-year breakdown.
Simple vs. Compound Interest
Simple interest is calculated only on the principal amount. Compound interest is calculated on the principal plus previously accumulated interest — meaning your money grows faster the longer it stays invested. This calculator uses compound interest, which is how most savings accounts, investments, and loans actually work.
What is Compounding Frequency?
Compounding frequency is how often interest is added to your balance within a year. More frequent compounding means slightly more interest over time:
- Annually — interest added once per year
- Semi-annually — twice per year
- Quarterly — four times per year
- Monthly — twelve times per year (most common for savings accounts)
- Daily — 365 times per year
The Compound Interest Formula
The formula used is: A = P × (1 + r/n)nt, where P is the principal, r is the annual rate (as a decimal), n is the number of compounding periods per year, and t is the number of years.
How to Use This Calculator
- Enter your starting principal (the amount you invest or deposit).
- Enter the annual interest rate as a percentage.
- Enter the number of years you want to calculate for.
- Choose how often interest compounds.
- Click "Calculate interest" to see your results.