Saving & investing
Compound Interest Calculator
Start with $10,000, add $300 a month, and earn 7% a year.
After 20 years you'd have about $196,665. You would have paid in $82,000 of your own money, and the other $114,665 is interest doing the work.
Change the numbers below. This assumes a steady return and monthly compounding, which real markets don't give you, so treat it as a projection, not a promise.
$196,665
balance after 20 years
■ you paid in $82,000 ■ interest $114,665
You pay in$82,000
Interest earned+$114,665
Balance$196,665
Monthly compounding
Where the growth comes from
Early on, almost all the balance is money you put in. Later, interest starts earning interest, and that's when the line bends upward. In this example the interest overtakes your own contributions somewhere in the later years, which is the whole point of starting sooner rather than later.
Balance over time
| Year | Paid in | Interest | Balance |
|---|---|---|---|
| 5 | $28,000 | $7,654 | $35,654 |
| 10 | $46,000 | $26,022 | $72,022 |
| 15 | $64,000 | $59,578 | $123,578 |
| 20 | $82,000 | $114,665 | $196,665 |
Monthly compounding, steady return assumed. Real returns vary year to year and are not guaranteed. This is a projection for planning, not financial advice.
Common questions
How much does $10,000 grow in 20 years?
At 7% a year with $300 added monthly, about $196,665. You'd have put in $82,000, and $114,665 of it is interest.
What is compound interest?
It's interest that earns its own interest. You get a return on your balance, and next period that return is part of the balance too, so the growth builds on itself.