How to use the Compound Interest Calculator
- Enter your starting amount and monthly contribution.
- Set the expected annual interest rate and number of years.
- Choose how often interest compounds.
- Review the final balance and the year-by-year breakdown.
Frequently asked questions
What is compound interest?
Compound interest is interest earned on both your original money and the interest it has already earned. Over long periods this snowball effect can be larger than your contributions.
What is the compound interest formula?
For a single deposit, A = P(1 + r/n)^(nt), where P is the principal, r the annual rate, n compounding periods per year and t the number of years.
What return should I assume?
High-yield savings accounts often pay a few percent a year; the long-run average for broad US stock indexes has historically been higher but with big year-to-year swings. Past returns don't guarantee future results.