Diagnostic Test Calculator

Calculate true/false positives & negatives from disease prevalence, sensitivity, and specificity

Real-World Examples Click to load values

%
%
%
Confusion Matrix
Test Positive
Test Negative
Has Disease
True Positive
475
4.75%
False Negative
25
0.25%
No Disease
False Positive
950
9.50%
True Negative
8,550
85.50%
Proportional Area Visualization
Test Positive
Test Negative
Has Disease
True Pos
475
4.75%
False Neg
25
0.25%
No Disease
False Pos
950
9.50%
True Neg
8,550
85.50%
Correct results (TP + TN)
Errors (FP + FN)
PPV
33.3%
Positive Predictive Value
NPV
99.7%
Negative Predictive Value
Accuracy
90.3%
(TP + TN) / Total
LR+
9.50
Positive Likelihood Ratio
LR−
0.06
Negative Likelihood Ratio
Disease+
500
Total with Disease
Correct
9,025
TP + TN
Errors
975
FP + FN
Formulas Used
TP = Diseased × Sensitivity
FN = Diseased × (1 − Sensitivity)
FP = Healthy × (1 − Specificity)
TN = Healthy × Specificity
PPV = TP / (TP + FP)
NPV = TN / (TN + FN)