See how a lump sum grows with compound interest. Enter your starting amount, the annual rate, the term in years and months, and how often interest compounds. You get the ending balance, total interest, the effective annual rate (APY), and a year-by-year growth table.
Formula
Compound interest grows the balance each period and then earns interest on that interest. For a starting amount P, annual rate r, n compounding periods per year, and t years:
A = P · (1 + r/n)^(n·t) (continuous: A = P · e^(r·t))
Effective annual rate (APY) = (1 + r/n)^n − 1
The total interest is simply the ending balance minus your initial amount.
Simple vs. compound interest
| $100 at 10% for 2 years | |
|---|---|
| Simple interest | $120 ($10 + $10) |
| Compound interest | $121 ($10, then $11) |
Examples
$10,000 · 5% · monthly · 10 years
A $10,000 deposit at 5% compounded monthly grows to about $16,470 after 10 years — roughly $6,470 of interest — at an effective annual rate of 5.116%.
10% compounded semiannually
A 10% nominal rate compounded twice a year produces an APY of 10.25%, so $1,000 becomes $1,102.50 after one year.