Can accuracy be negative?
Technically, if the error is greater than 100%, the formula would yield a negative accuracy, indicating a very poor measurement. However, accuracy is often treated as a magnitude or capped at 0% in some contexts.
Calculator
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Analysis
Interpretation of the current calculator output
Enter values to see detailed analysis and insights.
How to Use
Step-by-step instructions
- 1Enter the observed (measured) value.
- 2Enter the actual (true) value.
- 3The calculator will display the accuracy percentage and the percent error.
Accuracy Formula
Accuracy measures how close a measured value is to the true or accepted value. It is the complement of the percent error.
Accuracy % = 100% - |(Observed - Actual) / Actual| x 100%Variables:
ObservedThe measured or experimental valueActualThe true or theoretical valueExample
Lab Experiment
Inputs:
Observed:9.8
Actual:10.0
Steps:
- 1.Error: |9.8 - 10.0| / 10.0 = 0.2 / 10.0 = 0.02
- 2.Percent Error: 0.02 x 100 = 2%
- 3.Accuracy: 100% - 2% = 98%
Result:
98%
Frequently Asked Questions
Why can the actual value not be zero?
Percent error divides by the accepted value. When that value is zero, the relative percentage is undefined; use absolute error instead.
Is measurement accuracy the same as classification accuracy?
No. This calculator measures closeness to an accepted numeric value. Classification accuracy is correct predictions divided by all predictions and requires confusion-matrix counts.