Common Vacuum Unit Converter

How to use this vacuum unit converter

Vacuum gets quoted in different units depending on who you ask. Nash and Elmo Rietschle pump curves are usually in Torr or mbar absolute, most plant gauges read inches of mercury (inHg) vacuum, and process engineers often work in PSIA. Enter a value, choose the unit it is in, and the converter shows the same pressure in all six units.

Gauge vs. absolute: the most common mix-up

Absolute pressure is measured up from a perfect vacuum, so zero is the lowest value possible. Gauge vacuum is measured down from the atmospheric pressure around you, which is 29.92 inHg at sea level. A gauge reading of 28 inHg vacuum is about 1.9 inHg absolute, or roughly 49 Torr. Sizing a pump against the wrong one is one of the most common specification errors we see.

Elevation matters too. In Atlanta, at roughly 1,000 feet, atmospheric pressure is closer to 28.9 inHg, so the same gauge reading means a different absolute pressure than it would on the coast. When in doubt, specify absolute.

Quick reference at standard atmosphere

• 760 Torr = 29.92 inHg = 14.696 PSIA = 1,013.25 mbar = 1 atmosphere

• 1 inHg = 25.4 Torr = 33.86 mbar

• 1 Torr = 1.333 mbar = 1,000 microns

• 1 PSI = 51.7 Torr = 2.036 inHg

Need help sizing a vacuum pump?

E.W. Klein has sized and serviced vacuum systems across Georgia, Alabama, Tennessee, the Carolinas and the Florida panhandle since 1921. Send us your operating pressure and flow, and a Klein engineer will recommend the right Nash liquid ring or Elmo Rietschle pump for the job.