Percent Error Calculator
Calculate the percentage error between true and observed values for scientific measurements and experiments
Calculate Percent Error
Standard percent error can be positive or negative
The accepted, theoretical, or exact value
The measured, experimental, or approximated value
Error Analysis Results
Enter values to calculate percent error
Note: True value cannot be zero
Scientific Measurement Examples
Speed of Sound Measurement
True: 343 m/s, Observed: 329 m/s
Laboratory measurement of sound speed in air at 20°C
Gravitational Acceleration
True: 9.81 m/s², Observed: 9.75 m/s²
Physics experiment measuring gravitational acceleration
Chemical Concentration
True: 0.1 M, Observed: 0.098 M
Analytical chemistry concentration determination
Error Types
Percent Error
(TV - OV) / TV × 100%
Relative error as percentage
Absolute Error
|TV - OV|
Magnitude of difference
Relative Error
(TV - OV) / TV
Decimal form of percent error
Accuracy Guide
Understanding Percent Error
What is Percent Error?
Percent error is a measure of how far off a measurement or calculation is from the true or accepted value. It's expressed as a percentage and is commonly used in scientific experiments, engineering calculations, and quality control processes.
Formula Breakdown
Percent Error = (True Value - Observed Value) / True Value × 100%
- •True Value (TV): The accepted, theoretical, or exact value
- •Observed Value (OV): The measured, experimental, or calculated value
Interpreting Results
Positive Percent Error
When percent error is positive, it means the observed value is less than the true value. The measurement underestimated the actual value.
Negative Percent Error
When percent error is negative, it means the observed value is greater than the true value. The measurement overestimated the actual value.
Zero Percent Error
When percent error is zero, it means the observed value exactly matches the true value. This represents perfect accuracy.
Common Applications
Physics Experiments
Measuring gravitational acceleration, speed of light, or other physical constants.
Chemistry Analysis
Determining concentrations, reaction yields, or molecular weights in laboratory work.
Engineering Design
Validating calculations, testing prototypes, or quality control in manufacturing.
Statistical Analysis
Comparing model predictions with actual data or evaluating measurement precision.
Important Considerations
Sources of Error
- • Instrumental limitations
- • Human measurement error
- • Environmental conditions
- • Systematic biases
- • Random fluctuations
Improving Accuracy
- • Use more precise instruments
- • Take multiple measurements
- • Control environmental factors
- • Calibrate equipment regularly
- • Follow proper procedures