Compound Interest Calculator
- Interest earned
- $6,470.09
- Total deposits
- $10,000.00
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How to use it
- Enter your starting balance and how much you'll add each month.
- Enter the expected annual interest rate or return, and how often interest compounds.
- Choose the number of years to see your projected balance.
Examples
A one-time deposit
$10,000 at 5% compounded monthly grows to $16,470.09 after 10 years. Compounded yearly it reaches $16,288.95.
Saving every month
Start with $5,000, add $200 a month at 7% compounded monthly, and after 20 years you'd have about $124,379 — of which $53,000 is your own deposits.
How compounding works
Compound interest earns interest on previously earned interest. The more often it compounds, the slightly faster the balance grows: monthly compounding beats yearly at the same stated rate.
Monthly contributions are assumed to be made at the end of each month and grow at the same rate. Real investment returns vary year to year, so treat the result as a projection, not a guarantee.
balance = P × (1 + r/n)^(n×t) + contributions grown at the same rate
Frequently asked questions
What is the rule of 72?
Divide 72 by the annual rate to estimate how many years it takes money to double. At 6%, money doubles in about 12 years.
What rate should I use?
For a savings account, use its APY. For investments, many people test a few conservative rates; past average returns don't guarantee future ones.
Does this account for inflation or taxes?
No. To see growth in today's money, subtract the expected inflation rate from the interest rate as a rough adjustment.
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More in Money · Last reviewed October 2026