Using absolute pressure, if the pressure is 14.7 lbs, what is the gauge pressure?

Absolute pressure is measured from a perfect vacuum and includes atmospheric pressure. Gauge pressure, on the other hand, measures pressure relative to atmospheric pressure and does not include it. To convert absolute pressure to gauge pressure, atmospheric pressure (approximately 14.7 psi at sea level) must be subtracted from the absolute pressure value.

In this case, if the absolute pressure is 14.7 lbs (or psi), when you subtract the atmospheric pressure of 14.7 psi, the result is 0 psi. This means that at 14.7 psi absolute, there is no additional pressure above atmospheric pressure, leading to a gauge pressure of 0 psi.

Thus, the concept that connects these pressures clarifies why the gauge pressure is 0 psi when the absolute pressure equals atmospheric pressure.