ISO 1328-1 defines accuracy classes for cylindrical gears. Quality classes range from 0 (highest precision) to 12 (lowest). It specifies tolerances for pitch, profile, and helix deviations.

What quality class do I need?

Class 5-6: precision gearing (machine tools, instruments). Class 6-7: general engineering. Class 8-9: heavy machinery. Class 10-12: rough gearing. Most industrial gearboxes use class 6-8.

What is total pitch deviation (Fp)?

Fp is the maximum difference between the actual and theoretical cumulative pitch over all teeth. It reflects spacing accuracy of all teeth around the gear. Measured using gear measuring machines.

What is profile deviation?

Profile deviation measures how the actual tooth profile differs from the theoretical involute. It includes total profile deviation (Fα), profile form deviation (ffα), and profile slope deviation (fHα).

How are ISO 1328 tolerances calculated?

Tolerances depend on module (m), pitch diameter (d), and face width (b). Each quality class doubles the tolerance from the previous class. The formulas use geometric mean calculations based on these parameters.

Free Engineering Tool #095

Gear Accuracy Class Calculator

ISO 1328-1 gear accuracy tolerances. Enter module, pitch diameter, face width, and quality class to look up pitch deviation, profile deviation, and helix deviation tolerances.

ISO 1328-1Class 3–12Tolerances

Results

Quality Class

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Total Pitch Deviation F_p

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Single Pitch Deviation f_pt

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Total Profile Deviation F_α

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Total Helix Deviation F_β

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ISO 1328-1 Tolerance Formulas (Simplified)

Where K is the class multiplier: each quality step doubles the tolerance (K₅=1, K₆=2, K₇=4, …, K₁₂=128 relative to class 5).

Quality Class Application Guide

Class	Application	Typical Tolerance Scale
3–4	Master gears, measuring instruments	Finest
5–6	Machine tools, precision gearboxes, turbine gears	Precision
7–8	General industrial gearboxes, vehicle transmissions	Standard
9–10	Heavy machinery, mining, cement	Coarse
11–12	Rough gearing, agricultural, slow speed	Very coarse

Gear Accuracy Class Calculator | ISO 1328-1 | Free Online Tool

Published by Nikolai Shelkovenko on February 15, 2026 February 15, 2026

Results

ISO 1328-1 Tolerance Formulas (Simplified)

Quality Class Application Guide