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Investing

Compound Interest Calculator

See what your money could grow into, and how much of that ending balance is your own contributions versus the growth on top.

$
yrs
$
%
Required field
Total balanceiWhat the account is worth at the end: your initial amount, every deposit you made, and all the growth on top.
$0
Total contributionsiYour initial amount plus every deposit you make over the period. This is the money that came out of your pocket.
$0
Total interest earnediThe growth on top of what you put in. This is the part compounding creates for you.
$0

Estimates of future growth based on the figures you entered, not a promise of future returns. Real returns vary year to year and can be negative.

Growth over time

Stacked bars showing initial amount, contributions and interest earned by year

Initial amount Contributions Interest earned
Year-by-year breakdown
Year Contributions to date Interest earned Balance
📈 Compounding only starts once the money is invested. The growth above assumes the money is in the market, not sitting in cash. Our affiliate partner moomoo offers commission-free stock and ETF trading with fractional shares, so a smaller starting amount can still buy in. Fidelity, Vanguard, and Charles Schwab are other options worth comparing.
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Investing involves risk, including the possible loss of principal. This calculator is for education only and is not investment advice. Some links on this page may be affiliate links. Our recommendations are always based on our editorial judgment, not compensation.

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Compound Interest Calculator FAQ

Compound interest is interest that earns interest. Your balance grows, and that new, larger balance is what grows next. Simple interest works differently, because it only ever pays on your original deposit.

The effect starts slow. In the early years, most of your balance is money you paid in yourself. Given enough time, the growth can become the bigger share of the total.

Six fields drive the result. Here is what each one is asking for.

  • Initial amount. The money you are starting with today. Enter 0 if you have nothing invested yet and plan to build the balance from contributions alone.
  • Years of growth. How long the money stays invested. This is the biggest lever in the whole calculation, so it is worth trying a few lengths and comparing.
  • Contribution amount. What you add on a regular schedule, on top of your starting amount.
  • Contribution schedule. How often that amount goes in. Monthly means 12 deposits a year. Annually means one.
  • Expected annual return. The average yearly growth you expect on the money. Many long-term investors use 6% to 7% as a planning figure. Real returns move around a lot from year to year and can be negative.
  • Compounding frequency. How often earnings are added to your balance. Once they are added, those earnings start earning too.

Compounding has a standard formula. It shows what one starting amount could become at a given rate:

A = P(1 + r/n)nt
  • A the balance at the end
  • P your initial amount
  • r your annual return, written as a decimal
  • n how many times a year earnings are added
  • t the number of years invested

Regular deposits sit on top of that. The calculator walks through every period one at a time, so each deposit only earns from the date it lands.

Compounding frequency is how often earnings get added to your balance. Two accounts paying the same 5% can drift apart if one adds earnings monthly and the other adds them once a year.

Monthly compounding gives a lump sum 12 chances a year to grow instead of one. The gap is usually small next to your rate and your years invested. Deposit timing shifts it too, so change the setting above and see how much your own total moves.

When I ran the numbers at 7% a year, $150 a month for 30 years landed near $183,000. The same $54,000 paid in as $300 a month for 15 years landed near $95,000.

Same money in, very different endings. The extra years give the earliest deposits far longer to compound. Starting small and early is one option many people consider, and the amount can rise later.