How Compound Interest Calculator Works
Compound interest is calculated using A = P × (1 + rate ÷ 100 ÷ n)^(n × years), where P is the principal, n is the number of compounding periods per year, and the exponent covers the total number of periods over the full term. The interest earned is simply the final balance minus the original principal.
How to Use This Tool
- Enter the principal amount you're starting with.
- Enter the annual interest rate and the number of years.
- Choose how often interest compounds — annually, semi-annually, quarterly or monthly.
- Select Calculate to see the final balance and total interest earned.
Example
$5,000 invested at 5% annual interest, compounded monthly, for 3 years grows to about $5,807.36 — roughly $807.36 in interest, more than the $750 you'd earn with simple interest over the same period.
Helpful Tips
- More frequent compounding (monthly vs. annually) produces a slightly higher return at the same stated annual rate, since interest starts earning interest sooner.
- Small rate or time differences compound significantly over long periods — this is why starting to invest early matters.
- Compare this tool's result against the simple interest calculator to see the effect of compounding for yourself.
Frequently Asked Questions
Why does compounding frequency matter?
More frequent compounding means interest is added to the balance more often, so subsequent interest is calculated on a slightly larger amount each time, producing a higher final balance.
What's the difference between the annual rate and the actual return I earn?
The stated annual rate is a nominal rate. With monthly or more frequent compounding, your effective annual return ends up slightly higher than the nominal rate.
Can I use this for loans as well as investments?
Yes, the same compounding formula applies whether the balance is growing as savings or as a debt that accrues compound interest.
Does the calculator account for regular deposits or withdrawals?
No, this calculates growth of a single lump-sum principal only, with no additional contributions along the way.
This tool runs entirely in your browser. Your input is not uploaded to any server.