Compound Interest Calculator
Work out how a savings balance grows when interest is added at regular intervals, with an optional contribution at the end of each period. Shows the final balance, the interest earned and a yearly table.
Up to 2 decimal places, for example 1000 or 1000.50.
A percentage, for example 5 or 4.25. Up to 6 decimal places.
Can be a decimal, for example 2.5. Up to 150 years.
1 for yearly, 2 for half-yearly, 4 for quarterly, 12 for monthly, 365 for daily. Any whole number of 1 or more.
Added at the end of each compounding period, after interest. Leave as 0 for none.
Yearly table
Balance at the end of each year. A final row at a decimal year end is shown when the years are not a whole number.
| Year | Balance | Total contributed | Interest to date |
|---|
How it works
Each compounding period, the balance earns the annual rate divided by the number of periods per year, and any contribution is added at the end of the period:
balance after one period = balance before × (1 + rate ÷ (100 × periods per year)) + contribution
Applying that for every whole period gives the final balance. With no contributions it is the familiar formula: principal × (1 + rate ÷ (100 × periods per year)) to the power of (years × periods per year).
If the years are a decimal and do not end on a whole period, the leftover part of a period earns simple interest at the period rate for that fraction of the period. No contribution is added for the leftover part.
Interest earned is the final balance minus the total contributed (the principal plus every contribution made). The figures are illustrative only. They assume a fixed rate, no fees or tax, and contributions paid on time. They are not financial advice. Check the terms of any account or product before you decide.