Compound Interest Calculator
Enter a principal amount, interest rate, compounding frequency, and time frame to see how much your money could grow.
Last updated: September 5, 2026
Frequently asked questions
What's the formula for compound interest?
A = P(1 + r/n)^(nt) - where P is principal, r is the annual rate, n is compounds per year, and t is time in years.
How does compounding frequency affect growth?
More frequent compounding (daily vs. annually) produces slightly higher returns at the same stated rate, since interest starts earning interest sooner - though the difference is usually small at typical savings rates.
How much difference does starting a few years earlier make?
A significant one - because growth compounds on itself, money invested 5 or 10 years earlier at the same rate ends up substantially larger, not just proportionally larger, since the earlier contributions have more compounding periods working on them.
Is compound interest always better than simple interest?
Compound interest earns interest on both principal and previously earned interest, so it always outpaces simple interest (which only earns on the original principal) given enough time. The longer the time horizon and the higher the compounding frequency, the bigger the gap becomes.
How much does $10,000 grow to in 20 years at 6% compounded annually?
Using A = P(1 + r/n)^(nt) with P=$10,000, r=0.06, n=1, t=20: A = $10,000 × 1.06^20 ≈ $32,071 - roughly $22,071 in interest earned on top of the original principal.
Does this calculator account for regular contributions, or just a one-time lump sum?
This tool models a single lump-sum principal growing on its own - it doesn't add recurring monthly deposits. For growth that includes ongoing contributions, use a calculator built for regular deposits, such as an investment or savings calculator.
Is 'continuous compounding' the same as entering a very high compounding frequency?
Not exactly the same, but a close approximation - continuous compounding uses the formula A = Pe^(rt) and represents the theoretical limit as compounding frequency approaches infinity. Entering a very large number like 365 (daily) or higher for compounds per year gets you very close to that continuous-compounding result.