Compound Interest Calculator
A free, browser-based calculator. Runs entirely in your browser — no sign up, nothing stored.
Enter Values
How to use this calculator
- Enter the starting principal, the annual interest rate and the number of years.
- Optionally set how many times a year it compounds (defaults to monthly).
- Press Calculate to see the final balance and the interest earned.
How it works
Compound interest earns interest on both your original amount and the interest already added. The formula is A = P(1 + r/n)^(nt), where P is the principal, r the annual rate, n the times it compounds per year and t the number of years.
Compounding more often (monthly rather than yearly) slightly increases the final balance.
Worked example
$10,000 at 5% for 10 years, compounded monthly. A = 10,000 × (1 + 0.05/12)^(12×10) ≈ $16,470 — about $6,470 of interest.
Frequently asked questions
Does this include regular deposits?
No — it assumes a single lump sum with no further deposits or withdrawals.
Which compounding frequency should I pick?
Many savings accounts compound monthly; check your product's terms and conditions.
Related tools
Tip: Enter any known values to calculate the remaining results.
All calculations run in your browser. Your inputs are never saved or transmitted.