Compound Interest Calculator
Calculate compound interest growth over time
Calculator
Additional amount added each month
Breakdown
How to Use
Calculate compound interest growth
Enter initial amount
Input your starting principal amount
Set interest rate
Enter the annual interest rate
Choose time period
Select the investment duration in years
Add contributions
Optionally add monthly contributions
Compound Interest Formula
A = P(1 + r/n)^(nt)
Where A = final amount, P = principal, r = annual rate, n = compounds per year, t = years.
Frequently Asked Questions
Compound interest is interest earned on both the initial principal and accumulated interest. Unlike simple interest, your money grows exponentially. $10,000 at 7% compounded annually becomes $19,672 in 10 years vs $17,000 with simple interest.
More frequent compounding means more growth. Daily compounding beats monthly, which beats yearly. However, the difference is often small. $10,000 at 5% for 10 years: yearly = $16,289, monthly = $16,470, daily = $16,487.
The Rule of 72 estimates how long to double your money. Divide 72 by the interest rate. At 6% interest, money doubles in ~12 years (72÷6=12). At 8%, it doubles in ~9 years. It's a quick mental math shortcut.
At 7% annual compound interest, $10,000 becomes $38,697 in 20 years. At 10%, it grows to $67,275. At 5%, it reaches $26,533. Start early - time is the most powerful factor in compound growth.