inHg to PSI Converter
Convert inches of mercury to pounds per square inch — one inHg is 0.4912 psi. Results update as you type; exact factors shown.
One inch of mercury is 0.4912 pounds per square inch — see the exact factor, not a rounded rule of thumb.
How the inhg to psi 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 UK is metric for most trade and science but keeps miles, pints, stone and mpg (with the imperial gallon) in daily life.
Common pressure conversions
| From | To | Units |
|---|---|---|
| 1 inHg | 0.4912 psi | inch of mercury to pounds per square inch |
| 5 inHg | 2.4558 psi | inches of mercury to pounds per square inch |
| 10 inHg | 4.9115 psi | inches of mercury to pounds per square inch |
| 15 inHg | 7.3673 psi | inches of mercury to pounds per square inch |
| 20 inHg | 9.8231 psi | inches of mercury to pounds per square inch |
| 25 inHg | 12.2789 psi | inches of mercury to pounds per square inch |
| 29.92 inHg | 14.6953 psi | inches of mercury to pounds per square inch |
| 30 inHg | 14.7346 psi | inches of mercury to pounds per square inch |
| 40 inHg | 19.6462 psi | inches of mercury to pounds per square inch |
| 50 inHg | 24.5577 psi | inches of mercury to pounds per square inch |
| 60 inHg | 29.4693 psi | inches of mercury to pounds per square inch |
| 100 inHg | 49.1154 psi | inches of mercury to pounds per square inch |
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 |
| millimetre of mercury | mmHg | 133.322387415 pascal |
| inch of mercury | inHg | 3,386.389 pascal |
FAQFrequently asked questions about pressure conversion
How many psi is 1 inHg?
0.4912 psi.
What is 29.92 inHg?
14.696 psi — one standard atmosphere.
Where is inHg used?
US aviation altimeter settings and engine manifold vacuum.
What is 20 inHg of vacuum?
About 9.8 psi below atmospheric.
What is full vacuum in inHg?
29.92 inHg below atmospheric at sea level.
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 Physical Laboratory (NPL) — United Kingdom's national measurement authority.
Last checked: September 2026. Conversion factors are fixed by definition and do not change with tax years or regulations.