Gage R&R Calculator
Evaluate your measurement system — calculate repeatability, reproducibility, %GRR, and NDC
Gage R&R Calculator
Guide to Gage R&R Studies
What is Gage R&R?
Gage R&R (Repeatability and Reproducibility) is a measurement system analysis that quantifies the amount of variation in your measurement process. It separates measurement variation into:
- Repeatability: Same operator, same part, same gage (equipment variation)
- Reproducibility: Different operators, same part, same gage (operator variation)
Acceptance Criteria
| %GRR | NDC | Decision |
|---|---|---|
| ≤ 10% | ≥ 5 | Acceptable |
| 10% - 30% | 3 - 4 | Marginal |
| > 30% | < 3 | Unacceptable |
FAQ
What is NDC (Number of Distinct Categories)?
NDC represents how many distinct groups the measurement system can distinguish within the process variation. NDC ≥ 5 means the gage can resolve enough detail for process control. NDC of 1 means the gage cannot differentiate parts at all.
How should I enter the data?
Enter one row per trial, grouped by operator. For 2 operators × 3 trials on 5 parts, enter 6 rows of 5 values. The order is: Op1-Trial1, Op1-Trial2, Op1-Trial3, Op2-Trial1, Op2-Trial2, Op2-Trial3.
When is Gage R&R required?
IATF 16949 (automotive quality) mandates MSA for all measurement systems referenced in the control plan. AIAG MSA Reference Manual (4th edition) provides the standard methodology.