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Simple Interest Calculator

Our online tools will provide quick answers to your calculation and conversion needs. On this page, you can calculate simple interest over a given period of time viz., days, months and 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



Interest Rate (%):

Time Period:

Android: Use this interest calculator offline with our all-in-one calculator app.

Sample calculations

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


The simple interest formula:
SI = P×r×t
A = P+SI
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.

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