Compound Interest Calculator
Enter a starting balance, nominal annual rate, years and compounding frequency to calculate ending balance and interest earned.
Calculator arithmetic runs locally in your browser and does not require an API.
The interactive calculator loads here when JavaScript is enabled.
How to use Compound Interest Calculator
Choose how often interest is added to the balance. This tool models a single deposit, without regular contributions.
Formula and method
A = P(1 + r/n)^(nt). P is starting balance, r is annual rate as a decimal, n is compounds per year and t is years.
Understanding the results
Interest earned is ending balance minus principal. More frequent compounding increases growth at the same positive nominal rate; taxes, fees and withdrawals are excluded.
Worked example
A starting balance of 1,000 at 5%, compounded annually for 10 years, becomes 1,628.89, including 628.89 interest.
These are mathematical estimates, not financial advice or an offer of credit.
Frequently asked questions
What is compounding frequency?
It is how many times each year interest is added to the balance that earns subsequent interest.
Can I add monthly deposits?
Use the Investment Calculator for recurring contributions; this tool grows one starting amount.
Is 5% nominal the same as 5% effective?
Only with annual compounding. More frequent compounding gives a higher effective annual rate at a positive nominal rate.