Atmospheres to mmHg Converter
Convert standard atmospheres to millimeters of mercury — one atmosphere is exactly 760 mmHg. Results update as you type; exact factors shown.
One standard atmosphere is 759.9999 millimeter of mercurys — see the exact factor, not a rounded rule of thumb.
How the atmospheres to mmhg converter works
Pressures convert through the pascal (1 N/m²). One bar is exactly 100 kPa; a standard atmosphere is exactly 101.325 kPa; 1 psi is 6.894757 kPa (a pound-force on a square inch); 1 mmHg is 133.322 Pa by the conventional definition.
The US uses customary units (US gallon, short ton, °F) in daily life; NIST SP 811 gives the exact SI factors.
Common pressure conversions
| From | To | Units |
|---|---|---|
| 0.1 atm | 76 mmHg | standard atmospheres to millimeter of mercurys |
| 0.25 atm | 190 mmHg | standard atmospheres to millimeter of mercurys |
| 0.5 atm | 379.9999 mmHg | standard atmospheres to millimeter of mercurys |
| 0.75 atm | 569.9999 mmHg | standard atmospheres to millimeter of mercurys |
| 1 atm | 759.9999 mmHg | standard atmosphere to millimeter of mercurys |
| 1.5 atm | 1,139.9998 mmHg | standard atmospheres to millimeter of mercurys |
| 2 atm | 1,519.9998 mmHg | standard atmospheres to millimeter of mercurys |
| 3 atm | 2,279.9997 mmHg | standard atmospheres to millimeter of mercurys |
| 5 atm | 3,799.9995 mmHg | standard atmospheres to millimeter of mercurys |
| 10 atm | 7,599.9989 mmHg | standard atmospheres to millimeter of mercurys |
| 20 atm | 15,199.9978 mmHg | standard atmospheres to millimeter of mercurys |
| 50 atm | 37,999.9946 mmHg | standard atmospheres to millimeter of mercurys |
Units in this converter and their exact factors
| Unit | Symbol | One unit in pascals |
|---|---|---|
| pascal | Pa | 1 pascal |
| kilopascal | kPa | 1,000 pascal |
| megapascal | MPa | 1,000,000 pascal |
| bar | bar | 100,000 pascal |
| millibar (hectopascal) | mbar | 100 pascal |
| standard atmosphere | atm | 101,325 pascal |
| pound per square inch | psi | 6,894.757293168 pascal |
| millimeter of mercury | mmHg | 133.322387415 pascal |
| inch of mercury | inHg | 3,386.389 pascal |
FAQFrequently asked questions about pressure conversion
How many mmHg in an atmosphere?
Exactly 760, which is how the atmosphere was originally defined.
Where does 760 come from?
Torricelli measured atmospheric pressure in 1643 as a mercury column 760 mm tall.
What is half an atmosphere?
380 mmHg — roughly the pressure at 5,500 m altitude.
Is mmHg the same as torr?
Almost — they differ by about one part in seven million.
What is 2 atm in mmHg?
1,520 mmHg.
Where these figures come from
- BIPM — The International System of Units (SI Brochure, 9th edition) — definitions of the base and derived units.
- NIST Special Publication 811 — Guide for the Use of the International System of Units — the exact conversion factors used here.
- National Institute of Standards and Technology (NIST) — United States's national measurement authority.
Last checked: September 2026. Conversion factors are fixed by definition and do not change with tax years or regulations.