Convert Millimeters of Mercury to Pascals

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 Pascal (symbol: Pa) is a unit of pressure. The SI derived unit of pressure (and stress), formally defined as one newton per square meter (N/m²) by ISO 80000-4. Named for 17th-century French mathematician Blaise Pascal, whose 1647-48 Puy-de-Dôme experiment established that atmospheric pressure decreases with altitude. The pascal is a small unit — standard sea-level atmospheric pressure is exactly 101,325 Pa per the BIPM SI Brochure — so working engineering and meteorology use multiples: kilopascals (kPa) for everyday gauge pressures, megapascals (MPa) for material strength, hectopascals (hPa) for barometric readings (1 kPa = 10 hPa). The pascal is the universal SI reference for pressure across scientific publication (Physical Review, J. Fluid Mechanics), thermodynamic state tables (NIST REFPROP), and international engineering codes (ASME, EN, JIS). Converting Pa to psi is a divide-by-6894.76; Pa to bar is divide-by-100,000.

It belongs to the metric measurement system.

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