Static pressure is the water pressure acting on a watch when it is held stationary at a given depth. It increases linearly with depth: every 10 meters of water adds approximately 1 ATM of pressure to the case surfaces. A watch rated to 10 ATM is rated to withstand static pressure equivalent to 100 meters of depth — as measured under controlled, motionless test conditions.
Static pressure is the basis for standard water resistance ratings, including ATM figures and the ISO 6425 pressure test. It is the controlled variable used in manufacturer and certification testing. It is not the full picture of how pressure acts on a watch in real-world use — that is described by dynamic pressure.
In Practice
- ATM ratings are static pressure ratings. A watch rated to 100m / 10 ATM will resist 10 ATM of static pressure — but may not resist equivalent dynamic forces encountered at a fraction of that depth.
- Static pressure testing is the industry standard because it is reproducible and comparable across manufacturers. The limitation is that it does not account for impact, movement, or thermal shock — all of which generate forces in addition to static depth pressure.
- For practical daily use — hand-washing, swimming, showering — static pressure is the relevant variable. Dynamic pressure becomes significant for diving, high-impact water sports, or any use involving rapid submersion.
Related Terms
Dynamic Pressure · ATM Rating · Water Resistance · ISO 6425 · Pressure Testing
Read Next
For a full explanation of the difference between static and dynamic pressure — and what each means for how you use a replica watch near or in water — read: Replica Watch Water Resistance Guide