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Compound Interest Calculator

Enter a starting amount, an interest rate and a time to see how compounding grows your money. Add monthly deposits and choose how often interest compounds. The calculator shows the final balance, the interest earned and a table for each year.

Compound interest calculator

%
years

Use decimals for part of a year, such as 2.5.

Otherwise deposits are made at the end of each month.

Enter the interest rate and the time to see the growth.

How to use it

  1. Enter the starting amount and rate

    Type the amount you start with and the yearly interest rate. The starting amount can be 0 if you only plan to make deposits.

  2. Set time, deposits and compounding

    Enter the number of years, an optional monthly deposit and how often interest compounds. Choose whether deposits go in at the start or the end of each month.

  3. Read the growth

    See the final balance, how much you put in and how much came from interest, with a table showing each year.

Example: 10,000 at 5% for 10 years

With interest compounding monthly, 10,000 grows to 16,470.09 after 10 years. Compounding only once a year gives 16,288.95, so more frequent compounding earns slightly more. The 5% is an example, not a forecast.

The formula

With no deposits, compound growth follows one formula. Deposits are added month by month using the equivalent monthly rate.

Compound interest formula
PartMeaningExample
A = P × (1 + r/n)^(n×t)Final balance16,470.09
PStarting amount10,000
rYearly rate as a decimal0.05
nTimes compounded per year12
tYears10

Limits and limitations

  • Returns are assumed constant. Real investments rise and fall, and savings rates change, so treat the result as an illustration and not a forecast.
  • Tax, fees and inflation are not taken out. Your real purchasing power will grow less than the balance shown.
  • Deposits are monthly. Other deposit schedules are not modelled.
  • The result is an estimate for planning, not financial, tax or legal advice. Check the real figures with your lender, adviser or tax authority before you decide.

Frequently asked questions

What is compound interest?

It is interest earned on both your original amount and the interest already added. Over time that makes growth speed up compared with simple interest.

Does compounding more often make a big difference?

Only a small one at ordinary rates. Monthly instead of yearly compounding adds a little. The amount, the rate and the time matter far more.

How is this different from simple interest?

Simple interest pays on the original amount only. See the Simple Interest Calculator on this site to compare the two.

Is my information uploaded?

No. Your numbers is worked out by JavaScript running in your browser and is not sent to a server. The page itself still loads from a web server like any website. This site can load advertising or analytics scripts, but only after you accept them in the cookie notice. They are separate from the tools, which never pass the files or text you work with to them.

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