Simple Interest Calculator

Calculate the interest earned (or owed) on a flat-rate deposit or loan. Just enter the principal, annual rate, and time in years.

Interest earned
$1,500
Total balance
$11,500

The simple interest formula

I = P × r × t

P is the principal, r is the annual rate as a decimal, and t is time in years. The total balance is A = P + I = P(1 + rt).

Worked example

Deposit $10,000 at 5% simple interest for 3 years: I = 10,000 × 0.05 × 3 = $1,500. Final balance: $11,500.

Frequently asked questions

Related calculators