Interest Calculator

Find the final amount and the interest for simple or compound interest — compounded yearly, half-yearly, quarterly, monthly or daily.

Use a decimal or fraction for part of a year, e.g. 1.5

Result

Enter values and press Calculate to see the result.

Formula

I=PrtI = Prt

Simple interest: principal × yearly rate (as a decimal) × years.

A=P(1+rn)ntA = P\left(1 + \frac{r}{n}\right)^{nt}

Compound interest: the rate is split over n periods a year, and interest earns interest.

How to use this calculator

  1. Choose simple or compound interest and enter the starting amount, the yearly rate in % and the time in years.
  2. For compound interest, choose how often interest is added. Money is shown to 2 decimal places.

Worked example

1000 at 5% a year for 3 years, compounded yearly

r = 5% = 0.05, n = 1 and nt = 3.

A = 1000 × 1.05³ = 1157.625, which rounds to 1157.63.

Interest = 1157.63 − 1000 = 157.63; the effective annual rate is exactly 5%.

Frequently asked questions

What is the difference between simple and compound interest?

Simple interest is only paid on the starting amount. Compound interest is also paid on interest already added, so it grows faster.

What is the effective annual rate?

The rate you really earn in a year once compounding is included — also called the APY. Monthly compounding at 5% gives about 5.1162%.