# What is the formula of absolute pressure?

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## What is the formula of absolute pressure?

Hydrostatic pressure at any height below the water surface is calculated by P=hdg where h is the height below the open water surface, d is the density of water and g is the acceleration due to gravity. So if you want to calculate gauge pressure at height h then use formula P=hdg+P∘ where P∘ is atmospheric pressure.

## What are the three types of pressure?

When the local atmospheric pressure is greater than the pressure in the system, the term vacuum pressure is used. A perfect vacuum would correspond to absolute zero pressure. It is certainly possible to have a negative gauge pressure, but not possible to have a negative absolute pressure.

## What is vacuum gauge pressure?

A vacuum gauge is a pressure gauge used to measure pressures lower than the ambient atmospheric pressure, which is set as the zero point, in negative values (e.g.: −15 psig or −760 mmHg equals total vacuum).