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Compound interest calculator: Watch your money grow year by year

With compound interest, you also earn interest on the interest already added. Enter your starting amount, the annual percentage and the number of years. The calculator shows the final amount and the development along the way, so you can see what the term means.

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Applies to the amounts in this calculator.

The amount you start with.

USD

The annual interest or growth in percent.

%

How many whole years the amount stays invested.

years

Before tax. Interest is added once a year. Fixed annual growth is an assumption, not a promised return.

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Worked example
  • Explanation: Savings with interest
  • Starting amount: 100,000.00 USD
  • Percent per year: 7 %
  • Number of years: 20 years

Result

Final amount

386,968 USD

Growth

286,968 USD

Total growth

286.9684 %

Working

  1. S = K × (1 + r/100)ⁿ
    100,000.00 USD × (1 + 7/100)^20 = 386,968.45 USD
  2. growth = S − K
    386,968.45 USD − 100,000.00 USD = 286,968.45 USD
  3. total growth = 100 × (S − K) / K
    100 × 286,968.45 USD / 100,000.00 USD = 286.9684 %

The compound interest formula

Final amount = starting amount × (1 + rate)ⁿ, where n is the number of years. A rate of 7% is written as 0.07 in the formula.

Interest is calculated on the balance at the start of the year. The growth in money therefore gets larger year by year when the rate is positive and the money stays put. At 0%, the balance does not change.

Example: 100,000 at 7%

After the first year, the balance is 107,000. The second year gives 7,490 in interest, because the first 7,000 now also earns interest. After 20 years, the amount is 386,968.45 if the percentage is unchanged. That is before tax and any costs.

Annual interest and stock growth

On a savings account, the rate may be agreed for a period. For stocks, a fixed annual growth is a calculation assumption. The actual return can be both positive and negative from year to year.

The formula can be used for both types of calculation examples. A stock return that already includes reinvested dividends should not have dividends added again, though.

When you also deposit every month

This calculation starts from a single starting amount. If you put a fixed part of your salary into savings, the monthly savings calculator fits better. It takes into account that each deposit has its own time to grow.