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

LO: To calculate the percentage error.


  • What percentage represents.

  • The four basic operations of numeracy.

  • Error means the difference between your amount when compared to your expected amount.


  • That percentage error is the amount that an estimate or a quantity is off (different) 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