Absolute and Gauge Pressures


  • Pressure is always measured as a difference or with respect to a datum or reference.

  • Absolute pressure is measured relative to a perfect vacuum (0 atm), whereas gauge pressure is measured relative to atmospheric pressure (1 atm).

  • Absolute pressure is the sum of atmospheric pressure and the gauge pressure.

  • For example: 1 atm(gauge) = 2 atm(absolute).