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See how your investments grow over time with the power of compound interest.
Compound interest is interest earned on both your principal AND the accumulated interest from previous periods. Unlike simple interest, compounding accelerates your growth over time — this is what Einstein allegedly called "the eighth wonder of the world."
Formula: A = P × (1 + r/n)^(nt) — where P is principal, r is annual rate, n is compounds per year, and t is time in years.
Compounding frequency is how often interest is calculated and added to your balance. More frequent compounding (daily vs. annually) means slightly more growth over time, since you earn interest on interest sooner.
The Rule of 72 is a quick way to estimate how long it takes to double your money. Divide 72 by your annual interest rate. For example, at 8% per year, your money doubles in about 72 ÷ 8 = 9 years.
Regular contributions dramatically increase the end result. Even small monthly amounts added consistently can grow into large sums over long periods, thanks to compounding. Use the "With Contributions" tab to see the difference.
Yes, completely free. No signup, no download, and no limits on usage.
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