Free calculators and unit converters for general and everyday use.

Calculators » Finance » Simple Interest Calculator

Our online tools will provide quick answers to your calculation and conversion needs. On this page, you can calculate **simple interest (SI)** given principal, interest rate and time duration in days, months or years. We have made it easy for you to enter daily, weekly, monthly or annually charged interest rates. e.g., 2% interest per month, 5% per week, 10% per year

Result window

To find time period between two dates, use date duration calculator.

Download: Use this interest calculator offline with our all-in-one-calculator app for Android and iOS.

The simple interest formula:

SI = P×r×t

A = P+SI

Where,

A = Final amount

SI = Simple interest

P = Principal amount (Initial Investment)

r = Annual interest rate in percentage

t = Time period in years

When calculating simple interest by days, use the number of days for **t** and divide the interest rate by 365. Likewise, to calculate simple interest month-wise, use the number of months for **t** and divide the interest rate by 12.

The following examples will show you how to solve different variables involved in simple interest calculation.

**Example 1.** What is the simple interest on a loan of $300 for 4 months at 12% per year?

**Ans.** SI = P×r×t = 300×(12/100/12)×4 = $12

**Example 2.** Simple interest on $5000 over 4 years is $1800, what is the interest rate?

**Ans.** r = SI/(P×t) = 1800/(5000×4) = 0.09 = 9%

**Example 3.** If you borrow $1200 at a 5% annual interest rate, how long will it take for the total amount owed to reach $1300?

**Ans.** SI = 1300-1200 = 100

t = SI/(P×r) = 100/(1200*(5/100)) = 1.67 years or 20 months

**Example 4.** Find the principal if the simple interest in 14 days at 25% per annum is 100.

**Ans.** P = SI/(r×t) = 100/((25/100/365)*14) = 10428.57

© everydaycalculation.com