Compound Interest Calculator
Calculate how an investment or loan grows over time with compound interest, where interest is earned on both the principal and previously accumulated interest.
About this compound interest calculator
Compound interest is the engine behind long-term investment growth, and behind fast-growing debt if left unpaid. Understanding how it compounds over time is one of the most useful things to visualize before investing or borrowing.
How compound interest calculator works
The formula is: A = P × (1 + r/n)^(n×t), where P is principal, r is the annual rate (as a decimal), n is compounds per year, and t is years. For example, $10,000 at 8% compounded monthly for 10 years grows to roughly $22,196.
Common uses
- Projecting how a savings or investment balance grows over time
- Comparing different compounding frequencies
- Understanding how debt can grow if interest compounds unpaid
How to use this tool
- Enter the principal amount.
- Enter the annual interest rate.
- Enter the number of years.
- Enter how many times per year interest compounds.
- See the maturity value and total interest instantly.
What to know before using it
This assumes a fixed interest rate for the entire period; real investment returns typically vary year to year, so treat this as a projection tool, not a guarantee.
Privacy and browser-first processing
This tool runs entirely in your browser using JavaScript. Nothing you enter is uploaded or stored.
Frequently asked questions
What is the compound interest formula?
A = P × (1 + r/n)^(n×t), where P is principal, r is annual rate as a decimal, n is compounding frequency per year, and t is time in years.
Does more frequent compounding always mean more growth?
Yes, all else equal, more frequent compounding (monthly versus annually, for example) produces slightly more growth over the same period and rate.