Calculating Percentage Error (8)

Solve problems involving the use of percentages, including percentage increases and decreases and percentage error, with and without digital technologies(VCMNA276)

LO: To calculate percentage error.

  • What a percentage is.
  • The four basic operations of numeracy


  • That percentage error is the amount that an estimate or a quantity is off by compared to the actual calculated amount.


  • I can calculate the percentage error.

Percentage Error

Remember a percentage is a part of a whole and it usually out of 100.

Percentage error is the percentage difference between an estimated value when compared to the actual value.

In order to calculate percentage error follow these steps:

  1. Calculate the error (estimate/guess amount subtract the exact amount) – remember the error doesn’t matter if it’s positive or negative.

  2. Divide the error by the exact value.

  3. Multiply the answer by 100 to get a percentage amount.

Worked Example

Initial Guess (Estimate): 10 girls in the class

Actual Amount: 15 girls in the class

Error: 5 girls (10 – 15 = 5)

Formula: Error / Actual x 100

5 / 15 = 0.3333 x 100 = 33.3% error.

Calculating Percentage Error Videos