Hi Mariog

In the modern world (as I see it), pressure by definition is Force/Area. Those units are implied by lbf/in^2, kN/mm^2 -> kPa etc. Using inches of liquid disguises that fact, and - again as I see it - has no place in technology.

The metric system has already been abused by the term: kg/cm^2. A kg is a mass, not a force. The cm is used in the kitche*n and in dressmaking.