Convert Standard Atmospheres to Inches of Mercury
Convert Standard Atmospheres (atm) to Inches of Mercury (inHg) instantly and accurately.
Conversion Formula
inHg = atm × 29.92125558
About Standard Atmospheres
The standard atmosphere (atm) = exactly 101,325 Pa - defined by the 10th CGPM (1954) as the reference air pressure at sea level. Used to define STP (0°C and 1 atm) for gas law and thermochemistry. Chemical equilibrium constants (Kp), Henry's law solubility, and thermodynamic tables are tabulated at 1 atm. ISA aviation standard: sea-level 1 atm / 15°C, pressure halving every ~5.5 km. Diving physics: +1 atm per 10 m depth (fresh water) so 30 m = 4 atm absolute. Diamond formation in Earth's mantle: ~50,000 atm. 1 atm = 101,325 Pa.
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.
Quick Reference Table
| Standard Atmospheres (atm) | Inches of Mercury (inHg) |
|---|---|
| 1 atm | 29.9213 inHg |
| 2 atm | 59.8425 inHg |
| 5 atm | 149.606 inHg |
| 10 atm | 299.213 inHg |
| 25 atm | 748.031 inHg |
| 50 atm | 1496.06 inHg |
| 100 atm | 2992.13 inHg |