Convert Centimeters of Mercury to Standard Atmospheres
Convert Centimeters of Mercury (cmHg) to Standard Atmospheres (atm) instantly and accurately.
Conversion Formula
atm = cmHg × 0.01315789661
About Centimeters of Mercury
One centimetre of mercury (cmHg) = 10 mmHg ≈ 1,333.22 Pa. Historical medical and physiological literature used cmHg for intracardiac and intravascular pressures before mmHg became universal. Left ventricular systolic pressure ~12 cmHg; pulmonary artery systolic 2-3 cmHg. Some older European cardiological textbooks and pre-1970s surgical literature report pressures in cmHg. Central venous pressure, cerebral perfusion pressure, and intra-abdominal pressure are occasionally cited in cmHg in legacy datasets. 1 cmHg = 1,333.22 Pa.
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.
Quick Reference Table
| Centimeters of Mercury (cmHg) | Standard Atmospheres (atm) |
|---|---|
| 1 cmHg | 0.0131579 atm |
| 2 cmHg | 0.0263158 atm |
| 5 cmHg | 0.0657895 atm |
| 10 cmHg | 0.131579 atm |
| 25 cmHg | 0.328947 atm |
| 50 cmHg | 0.657895 atm |
| 100 cmHg | 1.31579 atm |