Compound Interest Calculator
See how your savings grow over time with regular deposits and compound interest.
Year-by-year table
| Year | Deposits | Interest | Balance |
|---|
How compound interest works
With compound interest you earn interest on your interest. Each period, the interest is added to your balance, so the next period's interest is calculated on a slightly bigger number. Over long stretches this snowballs, which is why starting early matters more than almost anything else.
A = P × (1 + r/k)k×t
Here P is the starting amount, r the yearly rate, k how many times a year interest compounds, and t the number of years. This calculator also adds your monthly deposit at the end of each month.
Example
Start with $5,000, add $200 a month, and earn 5% compounded monthly. After 10 years you'd have about $39,300. You put in $29,000, and roughly $10,300 is interest.
The rule of 72
To guess how long it takes money to double, divide 72 by the interest rate. At 6%, money doubles in about 12 years. At 9%, about 8 years.