Percent error formula is the absolute value of the difference of the measured value and the actual value divided by the actual value and multiplied by 100. Why percent error is required? Percent error calculation helps to know how close a measured value is to a true value. There may be a slight manufacturing error in measuring instruments. They can never be assumed to be exact. To get to know to what extend error is there, we go for this percent error formula.

## Formula for Percent Error

The formula to calculate Percent Error is:

Percentage Error = [(Approximate Value – Exact Value) / Exact Value] × 100 |

### Solved Example

**Example 1: **A scale measures wrongly a value as 8 cm due to some marginal errors. Calculate the percentage error if the actual measurement of the value is 12 cm.

**Solution:**

Given,

Approximate value = 8 cm

Exact value = 12 cm

Percentage Error = (Approximate Value – Exact Value / Exact Value × 100)

Percentage Error = (8 – 12)/12 × 100

= -33.3%

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