Sensitivity and Specificity Calculator
Sensitivity and specificity summarize classification against a chosen reference label. Predictive values are also included, but they depend on the prevalence in the evaluated sample.
How to use this calculator
- Enter all four integer counts from the same evaluation.
- Check that all inputs use the same units, period and population scope.
- Change one assumption at a time when comparing scenarios.
Formula used by sensitivity specificity calculator calculator
Sensitivity = TP/(TP+FN); specificity = TN/(TN+FP); PPV = TP/(TP+FP); NPV = TN/(TN+FN).
- Sensitivity = TP/(TP+FN); specificity = TN/(TN+FP); PPV = TP/(TP+FP); NPV = TN/(TN+FN).
- The results depend on the reference standard, thresholds and population. They do not determine whether a diagnostic test is suitable for an individual.
- The tool validates inputs and rounds displayed figures for readability; it does not validate assumptions against external records.
Worked examples
Worked example
A test has 82 true positives, 18 false negatives, 145 true negatives and 25 false positives.
Sensitivity = 82%; specificity = 145/170 ≈ 85.29%.
The calculator reports sensitivity, specificity and predictive values where denominators exist.
Understanding the result
Sensitivity and specificity summarize classification against a chosen reference label. Predictive values are also included, but they depend on the prevalence in the evaluated sample.
The results depend on the reference standard, thresholds and population. They do not determine whether a diagnostic test is suitable for an individual.
Important notes
The results depend on the reference standard, thresholds and population. They do not determine whether a diagnostic test is suitable for an individual.
Treat the result as an estimate from the entered assumptions. For commercial, statistical, engineering or health-related decisions, verify relevant specifications and professional guidance.
Frequently asked questions
Why do predictive values change between populations?
Positive and negative predictive values depend on prevalence as well as test performance.
Is overall accuracy enough?
No. Class balance and the cost of different errors may require additional metrics.
How should I interpret this result?
The results depend on the reference standard, thresholds and population. They do not determine whether a diagnostic test is suitable for an individual.
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Related explanations
Learn the method behind the number or compare the terminology before using the calculator.
- How to Calculate a Z-Score — Learn how a z-score shows how far a value is from the mean in standard-deviation units.
- How to Calculate Percentage Change — Learn the percentage change formula, how to calculate increases and decreases, and why the original value matters.
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This page provides a calculation tool plus explanatory information so you can understand what the result means and when the underlying method may not fit your situation.