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 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 |
|---|---|---|
| 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 |
| millimeter 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 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.