Convert Standard Atmospheres to Millimeters of Mercury
Convert Standard Atmospheres (atm) to Millimeters of Mercury (mmHg) instantly and accurately.
Conversion Formula
mmHg = atm × 759.9998917
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 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
| Standard Atmospheres (atm) | Millimeters of Mercury (mmHg) |
|---|---|
| 1 atm | 760 mmHg |
| 2 atm | 1520 mmHg |
| 5 atm | 3800 mmHg |
| 10 atm | 7600 mmHg |
| 25 atm | 19000 mmHg |
| 50 atm | 38000 mmHg |
| 100 atm | 76000 mmHg |