Compound Interest Calculator
Calculate the future value, interest earned, and effective annual rate on a lump sum with periodic compounding.
Future value–
Interest earned–
Effective annual rate (APY)–
How compound interest works
FV = P · (1 + r/m)^(m·t)
P is the starting amount, r the annual rate, m the number of times interest compounds per year, and t the number of years. Because each period's interest itself earns interest, the balance grows faster the more frequently it compounds.
APY = (1 + r/m)^m − 1
The effective annual rate (APY) is the real yearly growth once compounding is accounted for — useful for comparing accounts with different compounding frequencies. This calculator models a single lump sum with no further deposits or withdrawals.