Convert Inches of Mercury to Millimeters of Mercury
Convert Inches of Mercury (inHg) to Millimeters of Mercury (mmHg) instantly and accurately.
Conversion Formula
mmHg = inHg × 25.4
About Inches of Mercury
One inch of mercury (inHg) ≈ 3,386 Pa - the primary barometric pressure unit in US aviation and meteorology. ASOS weather stations, METARs, and altimeter settings in the US report in inHg. Standard sea-level pressure is 29.92 inHg. Altimeters are set to local QNH in inHg to maintain altitude reference. US barometers for home weather stations display inHg. Typical pressure range: 28.5-31.0 inHg in continental weather systems. Record low: ~25.70 inHg (Typhoon Tip, 1979). 1 inHg = 3,386.39 Pa.
About Millimeters of Mercury
One millimetre of mercury (mmHg) = pressure from 1 mm of mercury at 0°C and standard gravity = 133.322 Pa. Clinical medicine worldwide uses mmHg for blood pressure (normal ~120/80 mmHg) and for gas partial pressures in physiology: arterial O₂ ~95-100 mmHg; CO₂ ~40 mmHg; alveolar O₂ ~104 mmHg. Ophthalmologists measure intraocular pressure in mmHg (normal 10-21; glaucoma risk above 21). Vacuum equipment ratings are also given in mmHg. 760 mmHg = 1 atm. 1 mmHg = 133.322 Pa.
Quick Reference Table
| Inches of Mercury (inHg) | Millimeters of Mercury (mmHg) |
|---|---|
| 1 inHg | 25.4 mmHg |
| 2 inHg | 50.8 mmHg |
| 5 inHg | 127 mmHg |
| 10 inHg | 254 mmHg |
| 25 inHg | 635 mmHg |
| 50 inHg | 1270 mmHg |
| 100 inHg | 2540 mmHg |