Compound Interest Calculator
See how your money grows when interest earns interest. Add a starting amount and regular deposits, choose how often interest compounds, and see the balance year by year.
Future balance
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Interest earned
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In today’s money
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APY
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Effective yearly rate
Money doubles in
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Without new deposits
Growth inside a 401(k), IRA or Roth IRA isn’t taxed each year, so more of it keeps compounding. In a regular account, interest and gains may be taxed.
Growth over time
BalanceMoney paid inBalance in today’s money
Year by year
| Year | Deposits | Interest | Total paid in | Total interest | Balance |
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How to use the compound interest calculator
Enter what you have saved today, how much you plan to add each month, quarter or year, the yearly interest rate and how long the money will grow. The calculator shows your future balance, how much of it is interest, the APY and how long it takes your money to double.
Planning with real numbers
Open More options to raise your deposits each year, for example in line with pay rises, and to set inflation. The today’s money figure shows what the future balance would buy at today’s prices, which is the number that matters for goals like retirement or a home deposit. Download the year-by-year table as a CSV file to use in Excel or Google Sheets.
Assumptions
The rate stays the same every year, deposits are made on schedule, and taxes and fees aren’t included. Investment returns rise and fall, so treat results as estimates for planning, not a promise or financial advice.
Frequently asked questions
What is compound interest?
Compound interest is interest earned on your interest as well as on the money you put in. $10,000 at 5% a year grows to $10,500 after one year, then 5% of $10,500 is added the next year, and so on. After 10 years it is $16,288.95, not the $15,000 simple interest would give.
What is the compound interest formula?
For a lump sum, A = P × (1 + r/n)^(n×t), where P is the starting amount, r the yearly rate, n how many times a year interest compounds and t the number of years. $10,000 at 5% compounded monthly for 10 years is 10,000 × (1 + 0.05/12)^120 = $16,470.09. Regular deposits add PMT × ((1 + r/n)^(n×t) − 1) ÷ (r/n).
What is the difference between the interest rate and APY?
The interest rate is the yearly rate before compounding. APY (annual percentage yield) includes the effect of compounding during the year, so it is what you actually earn. 5% compounded monthly is an APY of 5.116%. Use APY to compare savings accounts.
How much does compounding frequency matter?
Less than people expect. $10,000 at 5% for 10 years becomes $16,288.95 with yearly compounding, $16,470.09 with monthly and $16,486.65 with daily. The rate, the time and how much you add matter far more.
How long does it take to double my money?
A quick estimate is the Rule of 72: divide 72 by the yearly rate. At 7% that is about 10.3 years. The exact figure is 10.2 years with yearly compounding and 9.9 years with monthly compounding; the calculator shows it for your rate.
What interest rate should I use?
For savings accounts and CDs, use the APY the bank quotes. For investments, use a cautious long-term average: returns go up and down from year to year, while this calculator assumes the same rate every year. Results are estimates, not a promise or financial advice.