Diagnostic Accuracy Calculator

Sensitivity, specificity, PPV, NPV, likelihood ratios and diagnostic odds ratio with CIs.

True positives

Test +, disease +

False positives

Test +, disease −

False negatives

Test −, disease +

True negatives

Test −, disease −

Prevalence for predictive values (optional)

Leave blank to use the prevalence in your sample.

Confidence level

Enter your values to see the result.

Confidence intervals for proportions use the Wilson score method; likelihood ratio and odds ratio intervals use the log method. Results use standard large-sample formulas and are meant to support, not replace, a statistician's review. Check the assumptions behind each method before you report the numbers.

Continue your work

2×2 Contingency Table Calculator — Test the 2×2 table for association.
Confidence Interval Calculator — Get intervals for any other proportion.

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Clear instructions

Find steps, examples and limitations below.

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How to use the Diagnostic Accuracy Calculator

Sensitivity, specificity, PPV, NPV, likelihood ratios and diagnostic odds ratio with CIs.

1 Enter true positives, false positives, false negatives and true negatives.
2 Optionally enter the prevalence in the population where the test will be used.
3 Read every accuracy measure with its confidence interval.

Example and practical tips

With 90 true positives, 30 false positives, 10 false negatives and 170 true negatives, sensitivity is 90%, specificity 85% and LR+ is 6.0.

Frequently asked questions

Why do PPV and NPV change with prevalence?

Predictive values depend on how common the condition is. The same test has a much lower PPV in screening than in a specialist clinic.

What are good likelihood ratios?

An LR+ above 10 or an LR− below 0.1 changes the probability of disease a lot; values near 1 add little information.

Which confidence interval method is used?

Wilson score intervals for proportions and log-based intervals for ratios, as recommended for diagnostic accuracy studies.