Percent Error Calculator
Calculate the percentage error between experimental (measured) and theoretical (accepted) values. Perfect for science experiments, lab reports, and measurement analysis.
Your measured or experimental result
The accepted or theoretical value
Most scientific calculations use absolute value for percent error
15.00%
Percent Error
|85 - 100| / 100 × 100% = 15.00%
Percent Error Formula
Percent Error = |Experimental - Theoretical| / |Theoretical| × 100%
Where:
- Experimental Value = Your measured result
- Theoretical Value = Accepted or true value
What Does Percent Error Mean?
- 0% error = Perfect accuracy
- Less than 5% = Excellent accuracy
- 5-10% = Good accuracy
- 10-20% = Fair accuracy
- 20%+ = Poor accuracy, check your method
Example Calculation
Example: In a lab experiment, you measure the acceleration due to gravity as 9.5 m/s². The accepted value is 9.8 m/s².
Percent Error = |9.5 - 9.8| / 9.8 × 100% = 3.06%
This is an excellent result (less than 5% error).
Accuracy Rating & Interpretation
Common Lab Scenarios
- Density measurements
- Reaction yields in chemistry
- Velocity and acceleration experiments
- pH measurements
- Temperature readings
Quick Reference Table
| Error Range | Accuracy Level |
|---|---|
| 0-2% | 🏆 Exceptional |
| 2-5% | ⭐ Excellent |
| 5-10% | ✅ Good |
| 10-20% | ⚠️ Fair |
| 20%+ | ❌ Needs Improvement |
Pro Tips
- Always use absolute value for percent error in science
- Negative error indicates your value is lower than accepted
- Positive error indicates your value is higher than accepted
- Check for systematic errors if error is consistently one direction
- Repeat measurements to reduce random error