Measurement of Uncertainty

Expanded Uncertainty Calculator

Calculate and report measurement uncertainty in compliance with ISO 15189:2022, GUM:2008, and JCGM 100 guidelines for accredited clinical laboratories.

GUM:2008 Compliant
ISO 15189:2022 Ready
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Input Parameters
Enter measurement data
Tip: Enter mean, SD, and replicates from internal QC. Bias is derived from EQA/PT results.
unit
unit
obs
%
≈ 95%
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Results will appear here
Enter your measurement parameters on the left and click Calculate MU to see the expanded uncertainty analysis.
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MU Calculation Formulas
GUM:2008 · ISO 15189:2022
ISO 15189:2022 — Clause 7.3.4
U
U = k × uc
Expanded Uncertainty (k=2 → ~95% confidence)
Expanded
uc%
uc% = √Σ(ui²)
Combined Standard Uncertainty (sum of squared components)
Combined
CV%
CV% = SD / x̄ × 100
Coefficient of Variation — Routine Imprecision (%)
Imprecision
Interpretation Guide
Based on Relative Expanded Uncertainty (%U)
✓
Low Uncertainty — %U ≤ 5%
Measurement uncertainty is within acceptable limits. Results can be reported with high confidence. Routine QC monitoring is sufficient.
⚠
Moderate Uncertainty — 5% < %U ≤ 10%
Acceptable in most routine clinical contexts. Review imprecision and bias sources. Results near clinical decision limits should be interpreted with caution.
✕
High Uncertainty — %U > 10%
Uncertainty exceeds typical laboratory quality goals. Investigate root causes — calibration, reagents, analyst technique, and instrument performance. Consider corrective action.
ISO 15189:2022 Key Clauses
Relevant MU requirements
Clause Requirement
7.3.3Laboratory shall determine MU for each examination
7.3.3 b)MU shall be estimated with k=2 unless otherwise justified
7.3.3 c)MU shall be evaluated at medically relevant concentrations
7.3.3 d)MU shall be reviewed if analytical performance changes
7.4.1.2MU shall be reported on request; available to users
Unit Converter
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