inHg to Millibar Converter
Convert inches of mercury to millibars — the two scales on an aviation altimeter. Results update as you type; exact factors shown.
One inch of mercury is 33.8639 millibar (hectopascal) — see the exact factor, not a rounded rule of thumb.
How the inhg to millibar 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 |
|---|---|---|
| 28 inHg | 948.1889 mbar | inches of mercury to millibar (hectopascal) |
| 28.5 inHg | 965.1209 mbar | inches of mercury to millibar (hectopascal) |
| 29 inHg | 982.0528 mbar | inches of mercury to millibar (hectopascal) |
| 29.5 inHg | 998.9848 mbar | inches of mercury to millibar (hectopascal) |
| 29.92 inHg | 1,013.2076 mbar | inches of mercury to millibar (hectopascal) |
| 30 inHg | 1,015.9167 mbar | inches of mercury to millibar (hectopascal) |
| 30.5 inHg | 1,032.8486 mbar | inches of mercury to millibar (hectopascal) |
| 31 inHg | 1,049.7806 mbar | inches of mercury to millibar (hectopascal) |
| 25 inHg | 846.5973 mbar | inches of mercury to millibar (hectopascal) |
| 26 inHg | 880.4611 mbar | inches of mercury to millibar (hectopascal) |
| 27 inHg | 914.325 mbar | inches of mercury to millibar (hectopascal) |
| 32 inHg | 1,083.6445 mbar | inches of mercury to millibar (hectopascal) |
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 millibars is 29.92 inHg?
1,013.25 mbar — standard atmospheric pressure.
Why do altimeters use both?
US aviation sets altimeters in inches of mercury; most of the rest of the world uses hectopascals.
What is a low altimeter setting?
Below about 29.5 inHg indicates a low-pressure system.
What is 1 inHg in mbar?
33.86 mbar.
What is QNH?
The altimeter setting that makes the instrument read airfield elevation on the ground — quoted in hPa or inHg depending on region.
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.