Compound Interest Calculator

Starting amount

Yearly interest rate (%)

Years

Interest is added

Regular deposit (optional)

Added at the end of every period above

This is a calculation from the numbers you enter, with a rate that never changes. It is not a forecast and not financial advice.

End balance: 16,470.09
Interest earned: 6,470.09
Total put in: 10,000.00

Year-by-year balance
Year	Start balance	Interest	End balance
1	10,000.00	511.62	10,511.62
2	10,511.62	537.79	11,049.41
3	11,049.41	565.31	11,614.72
4	11,614.72	594.23	12,208.95
5	12,208.95	624.63	12,833.59
6	12,833.59	656.59	13,490.18
7	13,490.18	690.18	14,180.36
8	14,180.36	725.49	14,905.85
9	14,905.85	762.61	15,668.47
10	15,668.47	801.63	16,470.09

Quick facts

Price: Free
Sign-up: Not required
Where it runs: On your device
Files uploaded: No
Limits: No fixed limit
Updated: October 2, 2026

Compound Interest Calculator works out the end balance and interest earned when interest is added to a sum again and again, with an optional regular deposit and a year-by-year table. It suits savers comparing accounts, students learning how compounding works, and anyone curious what a regular deposit adds up to. It is a calculation from the numbers entered, not a forecast or advice.

How to use

Type the Starting amount, in any currency. Use 0 if you start with nothing and plan to deposit.
Type the Yearly interest rate as a percentage, and the number of Years, a whole number.
Choose how often Interest is added: yearly, half-yearly, quarterly, monthly, weekly or daily.
Optionally type a Regular deposit. It is added at the end of every period you chose, after that period’s interest, so a monthly choice means a monthly deposit.
Read End balance, Interest earned and Total put in, then scroll the table to see each year’s start balance, deposits, interest and end balance.

Examples

10,000 at 5% a year for 10 years with interest added monthly grows to 16,470.09. The interest earned is 6,470.09, and 10,000.00 was put in. In the first year the interest is 511.62, which brings the balance to 10,511.62.

With interest added only once a year, the same sum reaches 16,288.95, so adding interest more often earns slightly more. Notice that each year in the table starts with the balance the year before ended with, which is why growth speeds up over time.

Limits

The rate is assumed to stay the same for the whole period; real accounts change their rates, charge fees and may tax interest, and none of that is included. The starting amount and the deposit may each be up to 1,000,000,000,000, the rate up to 100%, and the time from 1 to 100 whole years. Deposits are made at the end of each period, never at the start. A balance above 1,000,000,000,000,000 is refused as too large to show accurately.

FAQ

What is compound interest?

Compound interest is interest that is added to the balance, so the next interest is worked out on the larger amount. The yearly rate is divided by the number of periods in a year, and each period earns that share on the current balance.

How does the regular deposit work?

The deposit is added at the end of each period, after the interest for that period is added. With interest added monthly, it is a deposit every month. It is the same amount each time, and there is no option for deposits at the start of a period.

Is this a prediction of what my savings will be?

No. It is arithmetic on the numbers you enter, assuming the rate never changes. Actual returns vary, and fees, taxes and inflation are not counted, so treat the result as an illustration and not as advice.

Are my numbers stored or uploaded?

No. The calculation runs in this page on your device, and nothing you type is sent anywhere or kept.