Convert Millimeters of Mercury to Bar

The Millimeters of Mercury (symbol: mmHg) is a unit of pressure. A unit of pressure historically defined as the pressure exerted by a column of mercury exactly 1 millimeter tall at the standard acceleration of gravity (9.80665 m/s²) and the standard density of mercury (13,595.1 kg/m³ at 0 °C). The mmHg's contemporary definition rounds to exactly 133.322387415 Pa (NIST SP 811). Despite being non-SI, mmHg remains the international clinical standard for blood pressure measurement ("120 over 80" mmHg) per WHO and ESH guidelines, and is the default unit for intraocular pressure in ophthalmology (normal IOP 10-21 mmHg per Glaucoma Research Foundation) and intracranial pressure monitoring in neurology. Numerically the mmHg is almost identical to the torr (1 mmHg ≈ 1.0000007 torr — the difference is whether one uses the conventional density or the experimentally measured density of mercury). Barometric atmospheric pressure was historically quoted in mmHg before kPa/hPa adoption (760 mmHg = 1 atm = 101.325 kPa).

It belongs to the metric measurement system.

Millimeters of Mercury are commonly used in tire inflation, weather reporting, scuba diving, and engineering.

The Bar (symbol: bar) is a unit of pressure. A metric unit of pressure equal to exactly 100,000 pascals (100 kPa), approximately the average sea-level atmospheric pressure on Earth (1 atm = 1.01325 bar). Defined by IUPAC and accepted for use with the SI by the BIPM, the bar is not itself an SI-proper unit but is universally recognized in engineering. Bars are the default unit in European industry for compressed gas systems (compressed air at 6-10 bar shop pressure), hydraulics (mobile equipment at 200-400 bar working pressure), and chemical process plants. Car tire pressures in much of the world outside the US are specified in bar (a typical passenger car runs ~2.2 bar / 32 psi cold). Gauges on scuba cylinders (200 bar fill / ~2900 psi), brewery CO₂ tanks, fire suppression systems, and espresso machines (9 bar extraction pressure) all read in bar. 1 bar = 14.504 psi = 100 kPa = 0.9869 atm.

It belongs to the metric measurement system.

Bar are commonly used in tire inflation, weather reporting, scuba diving, and engineering.