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Percentage Error Calculator

Find the percentage error between measured and actual values. Free, fast, and accurate.

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Percentage Error

Find the error between measured and actual values

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How to Calculate Percentage Error

Percentage error measures how far a measured or experimental value is from the true or accepted value. The formula is:

|Measured − Actual| / Actual × 100

Example: You measure a length as 105 cm, but the actual length is 100 cm.

  1. Find the difference: 105 − 100 = 5
  2. Take the absolute value: |5| = 5
  3. Divide by the actual value: 5 ÷ 100 = 0.05
  4. Multiply by 100: 0.05 × 100 = 5%

Our calculator above automates this process. Enter both values and the percentage error appears instantly with a full step-by-step breakdown.

Real-World Examples

Lab Measurement

You measure a liquid as 48 mL, but the actual volume is 50 mL. Error: |48 − 50| / 50 × 100 = 4%.

Weight Scale

A scale reads 155 lbs, but the actual weight is 150 lbs. Error: |155 − 150| / 150 × 100 = 3.33%.

Temperature

A thermometer reads 99°F, but the actual is 98.6°F. Error: |99 − 98.6| / 98.6 × 100 = 0.41%.

Manufacturing

A part is made at 202 mm, target is 200 mm. Error: |202 − 200| / 200 × 100 = 1%.

Speed Reading

Radar reads 95 km/h, actual speed is 90 km/h. Error: |95 − 90| / 90 × 100 = 5.56%.

Ruler Measurement

You measure 9.8 cm, actual is 10 cm. Error: |9.8 − 10| / 10 × 100 = 2%.

Frequently Asked Questions

What is percentage error?
Percentage error measures how far a measured value is from the true or actual value, expressed as a percentage. Formula: |Measured - Actual| / Actual × 100.
How do I calculate percentage error?
Subtract the actual value from the measured value, take the absolute value, divide by the actual value, then multiply by 100. Formula: |Measured - Actual| / Actual × 100.
What is the percentage error if measured is 105 and actual is 100?
The percentage error is 5%. Calculation: |105 - 100| / 100 × 100 = 5/100 × 100 = 5%.
Can percentage error be negative?
No. Percentage error is always non-negative because it uses the absolute value of the difference. A value of 0% means the measured value matches the actual value exactly.
What is the difference between percentage error and percentage change?
Percentage error compares a measured value to a known actual value and is always positive. Percentage change compares two values over time and can be positive (increase) or negative (decrease).

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