Calculate compound interest on your investments. See how your money grows with different compounding frequencies and time periods.
Compound interest is the interest on a deposit or loan calculated based on both the initial principal and the accumulated interest from previous periods. Unlike simple interest, compound interest grows exponentially your money earns interest on interest.
Where
A quick mental math shortcut: divide 72 by your annual interest rate to estimate how many years it takes to double your money. At 12% → 6 years. At 6% → 12 years. This rule is accurate for rates between 6-10% and gets less precise at extremes.
Enter your numbers
Input principal amount, interest rate, compounding frequency, and time period.
See the growth
View the final amount, total interest earned, and a year-by-year growth table.
Compare scenarios
Adjust compounding frequency to see how monthly vs yearly compounding affects returns.
Investors
Project long-term returns on fixed deposits, mutual funds, or retirement accounts.
Students
Understand exponential growth in finance and mathematics courses.
Borrowers
See the true cost of credit card debt or compounding loans.
Financial advisors
Illustrate the power of starting early to clients with visual breakdowns.
Compound interest is interest calculated on both the initial principal and the accumulated interest from previous periods, causing exponential growth.
More frequent compounding (monthly vs yearly) results in slightly higher returns because interest is reinvested more often.
The Rule of 72 estimates how long it takes to double your money: divide 72 by your annual interest rate. At 8%, money doubles in about 9 years.