Compound Interest Calculator
Calculate compound interest with any compounding frequency and optional regular contributions.
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% p.a.
Final balance
–
- Total contributed –
- Interest earned –
- Effective annual rate –
- Simple interest for comparison –
A = P × (1 + r/n)n·t + monthly contributions compounded from the month they are made.
Year-by-year table
| Year | Contributed | Interest | Balance |
|---|
How to use the Compound Interest Calculator
- Enter the starting amount, annual interest rate and number of years.
- Choose the compounding frequency and any monthly contribution.
- Read the final balance and the year-by-year growth table.
Formula
Without contributions: A = P × (1 + r/n)n·t, where P is the principal, r the annual rate as a decimal, n the number of compounding periods per year and t the number of years. Monthly contributions are added at the end of each month and earn interest from the next compounding period. Simple interest, P × r × t, is shown for comparison.
Frequently asked questions
How much difference does compounding frequency make?
More frequent compounding gives slightly higher returns at the same nominal rate, but the effect is small compared with the rate and the time invested.
What is the effective annual rate?
It is the rate that, compounded once a year, gives the same result: (1 + r/n)ⁿ − 1. The calculator shows it.