Compound Interest Calculator
This free compound interest calculator shows how savings, CDs, or investments grow when interest is earned on both principal and previously earned interest — with daily, monthly, or annual compounding.
The compound interest formula
Where A is the final balance, P is the principal, r is the annual interest rate, n is the number of times interest compounds per year, and t is time in years. If you add regular monthly deposits, their growth is calculated separately using the future value of an annuity and added to the total.
Why compounding frequency matters
More frequent compounding (daily vs. annually) results in slightly higher returns because interest starts earning its own interest sooner. Compare with simple interest using our Interest Calculator or project portfolio growth with the Investment Calculator.
Frequently Asked Questions
What is compound interest?
Compound interest is interest earned on both your original principal and interest already added. This compound interest calculator shows the future balance for any rate, term, and compounding frequency.
Can I use this as a CD calculator?
Yes — enter the CD deposit, APY/rate, term, and compounding frequency to estimate maturity value.
Does monthly compounding beat annual?
Usually slightly yes, because interest is added more often. The difference grows over longer terms.