Percent error indicates your error when you measure something in an experiment. For instance, 1% error indicates that you’re very close to the accepted value and 40% error means you’re far away from the true value. There are certain easiest formulas which will help to calculate the error between the experimental value and the actual value. Let’s discuss this with the help of Australia assignment help experts.

Formula of Percent Error:

Percentage Error = ½E-T½½T½×100½

In the formula mentioned above ‘E’ indicates experimental value and ‘T’ for theoretical or actual value. Let’s discuss it with an example.

Sample 1:

The accepted distance between the earth and the moon is 100.5miles (E). You measure the distance as 90miles (T). What is the percent error?

The first thing you have to do is, insert your data in the formula.

= ½E-T½½T½×100½

Here E = 100.5 & T = 90

According to Formula,




=11.6666667% Percentage Error             

Now the question is how to calculate Percent Error?

Following these steps you’ll be able to solve these kinds of problems.

  • By subtracting one value from another you will get the error value.
  • Divide the error by the actual value. This may yield a decimal number.
  • Now convert the decimal number into a percentage by multiplying it with 100.
  • Add a Percentage symbol (%) to express your percent error value.

Let’s understand the formula by solving some problems.

Example 1:

Due to some marginal errors, your scale shows a wrong value as 9cm. Consider that the actual value of the scale is 15cm. Now calculate the percentage error using the percent error formula.


Experimental value is 9cm

Actual or Theoretical value is 15cm

Percent error = ½E-T½½T½×100½

Percentage error = (9-15)/15×100

= 6×100÷15

= 40% is the percentage error.

Example 2

In a hall, the organisers estimated 500 audiences. But 550 people came to see the program. Now calculate the per cent error using the formula.


Experimental value is 500

Actual or Theoretical value is 550

Percent error = ½E-T½½T½×100½

Percentage Error = (500-550)/550×100

= 50×100÷550

=9.0909% is the percentage error.

Example 3

A boy measured the perimeter of a rectangular plot to be 500cm. but the actual perimeter of the plot has been recorded as 520cm. now calculate the percent error of the boy’s measurement.


Given that,

Measured perimeter value = 500 cm

Actual perimeter value = 520 cm

Percent error = ½E-T½½T½×100½

Percentage error = (500-520)/520*100

= 20/520*100

= 3.8461% is the percent error

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