Calculate Compound Interest and Savings Growth
See how an initial amount grows when interest earns interest. Choose the compounding frequency, add regular monthly contributions at the start or end of each month, and follow the balance year by year.
How to calculate compound interest
- Enter the initial amount, the nominal annual interest rate and the number of years.
- Pick how often interest is compounded, from annually to continuously.
- Optionally add a monthly contribution and say whether it is paid at the start or end of each month.
- Review the future value, effective annual rate and year-by-year table, and download it as CSV.
Nominal rate vs effective annual rate
A 12% nominal rate compounded monthly earns 1% a month, which grows to 12.68% over a full year. That is the effective annual rate (EAR). More frequent compounding raises the EAR, and continuous compounding (eʳ − 1) is the upper limit. Compare offers by EAR, not by nominal rate. For interest that doesn't compound, use the Simple Interest Calculator.
Benefits
- Supports six compounding frequencies, including continuous compounding.
- Handles regular contributions with start- or end-of-month timing, as in recurring deposits and SIPs.
- Shows the effective annual rate so you can compare products fairly.
Limitations
- Assumes a constant rate with no taxes, fees or inflation. Real investment returns vary.
- Contributions are monthly and are made for whole months only. With non-monthly compounding they grow at the equivalent monthly rate, which can differ slightly from a bank's own crediting rules.
Privacy and security
Every number you type is calculated by JavaScript in this browser tab. Nothing is sent to a server or saved after you close the page.
Read our privacy policy for details about the site as a whole.
Frequently asked questions
What is the compound interest formula?
A = P × (1 + r/n)^(n·t), where P is the principal, r the annual rate as a decimal, n the compounding periods per year and t the years. With continuous compounding it becomes A = P × e^(r·t).
How are monthly contributions treated?
Each contribution earns interest at the monthly rate equivalent to your chosen compounding. Contributions paid at the start of the month earn one extra month of interest compared with contributions paid at the end.
Does daily compounding make a big difference?
Less than people expect. At 7% the effective rate is 7.229% with monthly compounding and 7.250% with daily compounding. The rate and the time invested matter far more.