Convert Inches of Mercury to Pascals

The Inch of Mercury (symbol: inHg) is a unit of pressure. A pressure unit defined as the pressure exerted by a 1-inch column of mercury at the standard density of mercury (0 °C) and the standard acceleration of gravity (≈ 3,386.389 Pa per NIST SP 811). Inches of mercury are the primary unit in US aviation for altimeter settings (the QNH datum is reported in inHg in METAR weather observations — "Altimeter 30.12 inHg" means 30.12 inHg corrected to mean sea level), US barometric weather reporting on consumer indoor weather stations and TV weather graphics, HVAC and refrigeration duct/return static pressure (often quoted as fractions of an inHg, e.g., 0.25 inHg = ~62 Pa), and some legacy automotive vacuum gauges measuring intake-manifold vacuum below atmospheric (a healthy engine reads ~18-22 inHg of vacuum at idle). Standard sea-level atmospheric pressure is 29.92 inHg = 1013.25 hPa = 101.325 kPa.

It belongs to the imperial measurement system.

Inches 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.