Calculate compound interest

How to use the compound interest calculator

1. Enter the initial principal and the nominal annual interest rate.
2. Choose the compounding frequency and the term in years.
3. If you'll add money every period, enter the contribution and whether it's made at the start or the end.
4. Review the final balance, the interest earned and the year-by-year growth.

Compound interest formula

A = P × (1 + r/n)^(n·t)

What each variable means

A

final amount

P

initial principal

r

nominal annual rate as a decimal

n

compounding periods per year

t

years

With contributions, each period adds the contribution (at the start or end, as chosen) and applies the period's interest r/n to the running balance.

Compound interest example

€10,000 at 5% a year compounded monthly for 10 years: A = 10,000 × (1 + 0.05/12)^120 = €16,470.09, of which €6,470.09 is interest.

Illustrative example with the data shown; not a guaranteed outcome.

Assumptions and limitations

• The interest rate stays constant over the whole term.
• Taxes, fees and inflation are not included.
• Interest is reinvested at the end of each compounding period.

Frequently asked questions