ⓘ Inch of mercury is a unit of measurement for pressure. It is used for barometric pressure in weather reports, refrigeration and aviation in the United States. I ..


ⓘ Inch of mercury

Inch of mercury is a unit of measurement for pressure. It is used for barometric pressure in weather reports, refrigeration and aviation in the United States.

It is the pressure exerted by a column of mercury 1 inch 25.4 mm in height at the standard acceleration of gravity. Conversion to metric units depends on the temperature of mercury, and hence its density; typical conversion factors are:

In older literature, an "inch of mercury" is based on the height of a column of mercury at 60 °F 15.6 °C.

1 inHg 60 °F = 3376.85 Pa

In English units: 1 inHg 60 °F = 0.489 771 psi, or 2.041 771 inHg 60 °F = 1 psi.


1.1. Applications Cooling systems

In air conditioning and refrigeration, inHg is often used to describe "inches of mercury vacuum", or pressures below ambient atmospheric pressure, for recovery of refrigerants from air conditioning and refrigeration systems, as well as for leak testing of systems while under a vacuum, and for dehydration of refrigeration systems. The low-side gauge in a refrigeration gauge manifold indicates pressures below ambient in "inches of mercury vacuum" inHg, down to a 30 inHg vacuum.

Inches of mercury is also used in automotive cooling system vacuum test and fill tools. A technician will use this tool to remove air from modern automotive cooling systems, test the systems ability to hold vacuum, and subsequently refill using the vacuum as suction for the new coolant. Typical minimum vacuum values are between 22 and 27 inHg.


1.2. Applications Vacuum brakes

Inches of mercury was the usual unit of pressure measurement in railway vacuum brakes.

  • manometric units are used to measure Starling forces. Inch of mercury Inch of water Pound per square inch Bar unit Torr BS 350: Part 1: 1974 Conversion
  • consolidate development and production, the Mercury Eight shared much of its bodyshell with Ford, distinguished by its 4 - inch 100 mm longer wheelbase. To further
  • a 125 - inch wheelbase 3 inches longer than the standard Mercury chassis In 1959, the Park Lane wheelbase was stretched to 128 inches 2 inches longer
  • are often measured in inches of water when at low pressure. This is in contrast to inches of mercury or pounds per square inch psi, lbf in2 for larger
  • 40 hp Mercury brought out the 4 in line, approximately 30 cubic inch Mark 30 30 horsepower engine for 1956, and produced versions of its TurboFour
  • The Bristol Mercury is a nine - cylinder, air - cooled, single - row, piston radial engine. Designed by Roy Fedden of the Bristol Aeroplane Company it was used
  • referred to as the four - inch flight The purpose of the MR - 1 flight was to qualify the Mercury spacecraft and the Mercury - Redstone launch vehicle for
  • Since the separation of Island Records, Motown, Mercury Records, and Def Jam Recordings combining the Island Def Jam Music Group, Mercury Records has been
  • The Mercury Monterey is a series of full - size cars that were manufactured and marketed by the Mercury division of Ford from 1952 to 1974. Deriving its
  • The Mercury Eight is an automobile that was marketed by the Mercury division of Ford between 1939 and 1951. The debut model line of the Mercury division