Compound Interest Calculator
Calculate how a lump sum grows over time with compound interest.
Final amount
- Interest earned
Worked example
A starting amount of 1,000 at 5% annual interest, compounded annually for 1 year, grows to 1,050: 50 in interest.
How we calculated this
This calculator demonstrates compound-interest mathematics; it does not predict investment returns or provide financial advice. Final amount = starting amount × (1 + annual rate ÷ compounding periods per year) raised to the power of (compounding periods per year × years). It assumes the entered rate stays exactly constant for the whole period. Results do not include taxes, fees, inflation, or variable rates, and no deposits or withdrawals are modelled. Real accounts and investments may behave very differently. This tool does not guarantee any return and does not recommend a savings account or investment. Time may be entered as a decimal number of years (e.g. 2.5); the formula applies exactly, without simulating individual partial compounding periods separately.
What this result means
The result is the final amount your starting principal grows to, and the total interest earned, over the term and compounding frequency you chose.
Assumptions and limitations
- No continuous compounding, no year-by-year breakdown table, and no chart — only the final amount and total interest earned are shown.