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Simple Interest Calculator

(no compounding of interest)
Time period or End date?
Use this simple interest calculator to calculate the interest on your savings or loan without compounding. That is to say that interest is only calculated on the principal, not on previously accumulated interest.

Disclaimer: Whilst every effort has been made in building this tool, we are not to be held liable for any damages or monetary losses arising out of or in connection with the use of it. Full disclaimer. This tool is here purely as a service to you, please use it at your own risk.

Calculating simple interest

The simple interest calculation is one that takes a sum of money (principal) and calculates regular interest on this amount only. This is a direct contrast to compound interest, where interest is calculated and accumulated with each period of time (so that you accumulate interest on interest). It is for this reason that the simple interest calculation is widely regarded as least advantageous to savers and most advantageous to borrowers. Should you wish to include compound interest in your calculations, give the regular savings calculator or loan calculator a try.

How to calculate your interest

To begin your calculation, enter your starting amount along with the annual interest rate and the start date (assuming it isn't today). Then, enter a number of years, months or days that the calculation is to run. Once you click the 'calculate' button, the simple interest calculator will show you:

  • The interest accrued
  • Your final value
  • The split of final value

Simple interest calculator formula

Our calculator uses the following formula:

FV = P(1 + rt)


  • FV = Final value (principal + interest)
  • P = Principal (starting amount)
  • r = Annual interest rate (as decimal)
  • t = time period (in years)

Should you wish to work out the total interest only, simply calculate FV - P.

Example interest calculation

If an amount of $5,000 is invested at a yearly interest rate of 5%, with no compounding (simple interest), its value after 3 years can be calculated as follows...

P = 5000.
r = 5/100 = 0.05 (decimal).
t = 3.

Plugging those figures into the formula gives the following:

FV = 5000 * (1 + (0.05 * 3))

FV = 5000 * 1.15 = 5750

The balance after 3 years is therefore $5,750.

If you have any problems using my simple interest calculator tool, or any suggestions, please contact me.