📐 Math
Percent Error Calculator
Calculate the percentage difference between an experimental (measured) value and a theoretical (exact/known) value to assess accuracy.
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Formula
Percent Error = ( |Experimental - Theoretical| / |Theoretical| ) × 100Experimental- The value you measured or estimated
Theoretical- The exact, accepted, or true value
Example
Calculating Measurement Error
You estimated a crowd size to be 200 people, but the exact ticket count was 250. Find the percent error.
- Subtract theoretical from experimental: 200 - 250 = -50.
- Take the absolute value: |-50| = 50.
- Divide by the absolute theoretical value: 50 / 250 = 0.2.
- Multiply by 100 to get a percentage: 0.2 × 100 = 20%.
- Result: 20% error.
Frequently Asked Questions
Generally, percent error is expressed as a positive number (using absolute value) to simply describe the magnitude of the error. However, omitting the absolute value lets you see the direction of the error (a negative sign means you underestimated).