Gage R&R calculator

Paste a crossed gauge study: each operator measures the same parts several times. The tool calculates repeatability (EV), reproducibility (AV), gage R&R (GRR), part variation (PV), %GRR, the number of distinct categories (ndc) and, if you enter the tolerance, %GRR of tolerance. A fictional example is loaded (3 operators, 10 parts, 3 trials).

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Measurements: one block per operator, separated by an empty line; one line per part (same order for every operator); trials separated by spaces

Tolerance width USL − LSL (optional)

3 operators × 10 parts × 3 trials

Source	Std. dev.	% of TV
Repeatability (EV)	0.1018	8.9 %
Reproducibility (AV)	0.1323	11.6 %
Gage R&R (GRR)	0.1669	14.6 %
Part variation (PV)	1.1277	98.9 %
Total variation (TV)	1.1400	–

%GRR 14.6 % (10 to 30 %) · ndc 9

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How it calculates

Average and range method with AIAG MSA 4th edition constants K1 (trials), K2 (operators) and K3 (parts).
EV = R̄ × K1, where R̄ is the average range of the repeated trials.
AV = √((X̄diff × K2)² − EV² ÷ (parts × trials)); if the term under the root is negative, AV is set to 0.
GRR = √(EV² + AV²), PV = Rp × K3 (Rp = range of the part averages), TV = √(GRR² + PV²).
%GRR = 100 × GRR ÷ TV; ndc = 1.41 × PV ÷ GRR, rounded down; %GRR of tolerance = 100 × 6 × GRR ÷ tolerance width.
Ranges above D4 × R̄ are flagged so you can check those readings first.

Limits and assumptions

Assumptions: a crossed study, every operator measures every part the same number of times, parts are listed in the same order for each operator, and the parts cover the process range (otherwise PV and %GRR are misleading). Limits: 2–3 operators, 2–10 parts, 2–3 trials. This is the average and range method only, not ANOVA, so it does not separate an operator × part interaction; results can differ slightly from ANOVA-based software. Common guidance is under 10 % usually acceptable, 10 to 30 % may be acceptable depending on the application, and over 30 % usually not, with ndc of 5 or more; your customer may set other criteria. Advisory only: verify against your own procedures and your customer's requirements.

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