What Is a Watch Movement Accuracy Standards: COSC vs ISO vs Manufacturer
Author: Funny Items
Release time: 2026-08-20 01:48:44
View number: 13
The Accuracy Benchmarks
Watch accuracy standards define how precise a movement must be. Here are the main certifications.
Accuracy Standards
| Standard | Accuracy | Issuing Body |
|---|---|---|
| COSC | -4 to +6 sec/day | Swiss COSC |
| ISO 3159 | -4 to +6 sec/day | ISO |
| Seiko | -20 to +40 sec/day | Seiko |
| Rolex Superlative | -2 to +2 sec/day | Rolex |
What This Means
- COSC is the Swiss industry standard
- Seiko is more relaxed but reliable
- Rolex exceeds all standards
Funny Items Movements
The NH35 and NH34 are rated -20 to +40 sec/day but often perform much better when regulated.