Gauge R&R calculator
The AIAG MSA manual’s example study, three appraisers measuring ten parts three times, gives a gauge R&R of 26.7 % of the total variation and 5 distinct categories: may be acceptable, depending on the use. Paste your own readings, one line per appraiser and trial, for repeatability, reproducibility and part variation by the Average and Range or ANOVA method, with each range checked against the control limit. Or check whether a measured value, with its uncertainty, proves a part in or out of tolerance.
May be acceptable (10 to 30 %)
- %GRR
- GRR, EV, AV
- 0.3058 · 0.2019 · 0.2297σ
- PV, TV
- 1.1046 · 1.1461σ
- Distinct categories
- 5 (5.09)
- %GRR of tolerance
- Enter a tolerance
- Ranges over UCL
- B part 4: 1.02
How it’s calculated
EV = R̿·K1; AV = √((X̄diff·K2)² − EV²/(n·r)), 0 if negative; GRR = √(EV² + AV²); PV = Rp·K3; TV = √(GRR² + PV²). Each is a standard deviation, so the percentages of TV do not add up to 100. ndc = 1.41·PV/GRR, cut to a whole number. Against the tolerance, %GRR = 100·6·GRR/TOL. One line per appraiser and trial (A1, A2, A3, then B), the parts across.
Appraisers
| Appraiser | Average X̄ | Average range R̄ | Largest range |
|---|---|---|---|
| A | 0.1903 | 0.1840 | 0.35 |
| B | 0.0683 | 0.5130 | 1.02 |
| C | -0.2543 | 0.3280 | 0.67 |
What does %GRR mean?
It is the gauge’s own spread, repeatability and reproducibility together, as a share of the spread it has to tell apart: the parts’ total variation, or the tolerance. Under 10 % the gauge is generally fine; 10 to 30 % may be acceptable for some uses; over 30 % it needs improving. Each component is a standard deviation, so the percentages do not add up to 100. The number of distinct categories says how many groups of parts the gauge can reliably tell apart: five or more for process control.