What is the gauge pressure if the absolute pressure is 400 kPa?
To determine the gauge pressure when given the absolute pressure, you need to know the atmospheric pressure as well. Gauge pressure is the pressure above atmospheric pressure.
To calculate gauge pressure, subtract the atmospheric pressure from the absolute pressure.
For example, if the absolute pressure is given as 400 kPa and the atmospheric pressure is 101.3 kPa (standard atmospheric pressure at sea level), the gauge pressure would be:
Gauge pressure = Absolute pressure - Atmospheric pressure
Gauge pressure = 400 kPa - 101.3 kPa
Gauge pressure = 298.7 kPa
Therefore, the gauge pressure would be 298.7 kPa.