How to use Compound Interest Calculator
- Enter your starting amount, the annual interest rate and the number of years.
- Choose how often the interest is compounded.
- Optional: add a monthly deposit and say whether it is paid at the start or the end of the month.
- Read the final balance and the yearly growth table.
About this tool
Without deposits the balance is P × (1 + r ÷ n)n × t, where P is the starting amount, r the annual rate, n the number of compounding periods per year and t the number of years. With monthly deposits the calculator works month by month, using the monthly rate that is equivalent to your chosen compounding frequency.
The result assumes a fixed rate and no tax, fees or inflation, so real returns will differ. Time is rounded to whole months. This is an estimate for planning only, not financial advice. Check real figures with your bank or lender.
Privacy: This tool runs in your browser. What you type or choose is not sent to a server by this website.
Common questions
What is the difference between compound and simple interest?
Simple interest is only paid on the original amount. Compound interest is paid on the original amount plus the interest already earned, so growth speeds up over time.
Does compounding more often make a big difference?
Only a small one. Going from yearly to monthly compounding adds a little; the rate and the time matter far more.
Why is my bank balance different?
Banks may use different compounding dates, variable rates, fees or tax. Use this as a guide.