Interest Calculator — simple and compound interest

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สูตร

I = Prt

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

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

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

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

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%.

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

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