Gage R&R (MSA) Calculator

Inputs are comparable standard-deviation components from a completed measurement study.

This selection changes review context only. Formulas and example inputs stay unchanged. Check the model assumptions and applicability for the actual process.

Identify the actual asset, process, work boundary, source documents, units and assumptions. Confirm that the selected model or template applies before using its results.

1 Inputs

Minimum: 0

Minimum: 0

Minimum: 0.0001

2 Results

%GR&R (study variation)
33.9%
Distinct categories (ndc)
3
%EV / %AV
28.2% / 18.8%
%PV (part)
94.1%
GRR = √(EV²+AV²); TV = √(GRR²+PV²); ndc = floor(1.41PV/GRR)
Inputs are comparable standard-deviation components from a completed measurement study. This combines them; it does not estimate them from readings. Review study design, part range and the measurement requirement before accepting the gauge.

Worked example

Example values are illustrative. Replace them with your measured data.

InputValue
Equipment variation (EV / repeatability)0.3 σ
Appraiser variation (AV / reproducibility)0.2 σ
Part variation (PV)1 σ

%GR&R (study variation): 33.9%

Related tools

About this calculator

How it works

You enter equipment variation (repeatability), appraiser variation (reproducibility) and part variation, each as a standard deviation from a Gage R&R study. GR&R = √(EV² + AV²), total variation TV = √(GR&R² + PV²), %GR&R = 100 × GR&R ÷ TV, and distinct categories ndc = floor(1.41 × PV ÷ GR&R).

Worked example (illustrative inputs)

EV 0.30, AV 0.20, PV 1.00: GR&R = √0.13 ≈ 0.361, TV ≈ 1.063, %GR&R ≈ 33.9%, ndc = floor(3.9) = 3.

How to read the result

Under the AIAG guideline the tool applies, below 10% is acceptable, 10–30% conditional and above 30% unacceptable; ndc should be 5 or more. 33.9% with ndc 3 means the gauge cannot reliably tell parts apart. Compare %EV and %AV to see whether the gauge or the method is the larger source.

When to use it

Use it after running a Gage R&R study, before trusting the gauge for SPC or capability work.

À propos de ce calculateur

Traduction (brouillon) — à relire.

Fonctionnement

Vous saisissez la variation équipement (répétabilité), la variation opérateur (reproductibilité) et la variation pièce, chacune en écart-type issu d'une étude R&R. GR&R = √(EV² + AV²), variation totale TV = √(GR&R² + PV²), %GR&R = 100 × GR&R ÷ TV, et nombre de catégories distinctes ndc = partie entière de 1,41 × PV ÷ GR&R.

Exemple chiffré (valeurs d'illustration)

EV 0,30, AV 0,20, PV 1,00 : GR&R = √0,13 ≈ 0,361, TV ≈ 1,063, %GR&R ≈ 33,9 %, ndc = partie entière de 3,9 = 3.

Lire le résultat

Selon la règle AIAG appliquée par l'outil, moins de 10 % est acceptable, 10–30 % conditionnel et plus de 30 % inacceptable ; ndc doit valoir 5 ou plus. 33,9 % avec ndc 3 signifie que l'instrument ne distingue pas les pièces de façon fiable. Comparez %EV et %AV pour savoir si l'instrument ou la méthode pèse le plus.

Quand l'utiliser

Utilisez-le après une étude R&R, avant de vous fier à l'instrument pour la MSP ou une étude de capabilité.

حول هذه الحاسبة

ترجمة (مسودة) — للمراجعة.

طريقة الحساب

تُدخل تباين الجهاز (التكرارية) وتباين المُقيِّم (إعادة الإنتاج) وتباين القطع، كلًّا كانحراف معياري من دراسة Gage R&R. ‏GR&R = √(EV² + AV²)، والتباين الكلي TV = √(GR&R² + PV²)، و%GR&R = 100 × GR&R ÷ TV، وعدد الفئات المميزة ndc = الجزء الصحيح من 1.41 × PV ÷ GR&R.

مثال محسوب (قيم توضيحية)

EV ‏0.30 وAV ‏0.20 وPV ‏1.00: ‏GR&R = √0.13 ≈ 0.361، وTV ≈ 1.063، و%GR&R ≈ 33.9%، وndc = الجزء الصحيح من 3.9 = 3.

قراءة النتيجة

وفق إرشاد AIAG الذي تطبّقه الأداة: أقل من 10% مقبول، و10–30% مشروط، وأكثر من 30% غير مقبول؛ وينبغي أن يكون ndc ‏5 فأكثر. ‏33.9% مع ndc ‏3 يعني أن الجهاز لا يميّز القطع بموثوقية. قارن %EV و%AV لمعرفة هل الجهاز أم الطريقة هو المصدر الأكبر.

متى تستخدمه

استخدمها بعد إجراء دراسة Gage R&R، قبل الاعتماد على الجهاز في ضبط العمليات إحصائيًا أو دراسات القدرة.

In one line

Inputs are comparable standard-deviation components from a completed measurement study. This combines them; it does not estimate them from readings. Review study design, part range and the measurement requirement before accepting the gauge.

Worked example

EXAMPLE

Illustrative values (the calculator defaults), not data from a real site.

Inputs
Equipment variation (EV / repeatability)0.3 σ
Appraiser variation (AV / reproducibility)0.2 σ
Part variation (PV)1 σ
Results
%GR&R (study variation)33.9%
VerdictUnacceptable
Distinct categories (ndc)3
%EV / %AV28.2% / 18.8%
%PV (part)94.1%

Frequently asked questions

How do I get EV, AV and PV values to enter here?

These come from a formal Gage R&R study — typically 2 to 3 operators each measuring the same 10 parts 2 to 3 times in random order, analyzed with ANOVA or the average-and-range method, often in software like Minitab. This calculator takes the resulting standard deviations as inputs rather than raw measurement data.

What is an acceptable %GR&R?

Under the AIAG guideline, below 10% is acceptable, 10 to 30% is conditionally acceptable depending on the measurement's cost and importance, and above 30% is considered unacceptable — the gauge, fixture or method needs improvement before the data can be trusted for process decisions.

Why is ndc important if %GR&R already looks fine?

%GR&R and ndc measure related but distinct things — %GR&R is about how much noise the measurement system adds, while ndc is about resolution, how many truly different groups it can tell apart. A system can pass on %GR&R yet still have too few distinct categories to support tight process control if part-to-part variation is small relative to the gauge's noise.

What's the difference between repeatability and reproducibility?

Repeatability (EV) is the variation you see when the same person measures the same part multiple times with the same gauge — it reflects the equipment itself. Reproducibility (AV) is the additional variation that shows up between different operators measuring the same part — it reflects differences in technique, training or fixturing.

My %GR&R is high — where should I focus improvement first?

Compare %EV and %AV in the results. If EV dominates, the gauge, fixture or measurement method itself needs attention (calibration, wear, fixture design). If AV dominates, the issue is more likely operator technique or training, and standardizing the measurement procedure across operators usually helps most.

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