Hello.

I am designing a housing for a pressure sensor and I am a bit confused.
Some places on the internet O-ring squeeze ratio is expressed as the amount of o-ring squeeze divided by the o-ring cross section.
Other places it is expressed as the amount of squeeze divided by groove depth.

These two methods of calculation give very different answers.
My O-ring is 1.778mm thick and the groove is 1.325mm deep.
The first method gives a squeeze ratio of 25.5%, the other 34%.

Which of these is the correct way?