Bar To Inches Of Mercury Converter
Convert pressure between bar and inches of mercury, with hPa, psi, mmHg and standard-atmosphere cross-checks for weather, vacuum and instrument readings.
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Quick Answer
One bar is exactly 100,000 pascals. One conventional inch of mercury is 3,386.389 pascals. Dividing those values gives 1 bar = 29.5299801647 inHg. The reverse factor is 1 inHg = 0.03386389 bar. This converter uses those factors for every result and then rounds only the final display.
Inches of mercury appear in barometers, aviation altimeter settings, some vacuum instruments and US weather reports. Bar is common on European pressure gauges, compressors, pumps and tyre equipment. The units can describe the same pressure, but the surrounding wording matters: absolute pressure, gauge pressure, vacuum below atmosphere and altimeter settings are not interchangeable just because the arithmetic is the same.
Formula And Steps
1 bar = 100,000 Pa
1 inHg = 3,386.389 Pa
inHg = bar x 29.5299801647
bar = inHg x 0.03386389
Pressure unit conversion is safest when both units are linked back to pascals, the SI pressure unit.
For bar to inHg, multiply by 29.5299801647. For inHg to bar, multiply by 0.03386389.
Keep the intermediate factor exact enough, then round the displayed result to match the source instrument.
Write whether the source is absolute, gauge, vacuum or weather pressure. The unit alone may not be enough.
Using inHg In Weather, Vacuum And Instruments
Weather and aviation users often see standard sea-level pressure written as 29.92 inHg, 1013.25 hPa or 1.01325 bar. NOAA describes standard air pressure at sea level as 29.92 inches of mercury. That is close to, but not the same as, 1 bar. If a pressure gauge says 1.000 bar, it converts to about 29.530 inHg, while one standard atmosphere converts to about 29.921 inHg.
Vacuum work needs extra care. A vacuum reading in inches of mercury may be stated as inches below atmospheric pressure, not absolute pressure. A pump catalogue, refrigeration note or workshop gauge may therefore mean “inHg vacuum” rather than “inHg absolute”. The converter changes unit size only. It does not decide whether the reading is referenced to vacuum, atmosphere or local pressure. When reporting a safety-critical pressure, copy the full label from the instrument.
Bar To Inches Of Mercury Conversion Table
| bar | inHg | Common Check |
|---|---|---|
| 0.1 bar | 2.953 inHg | Low pressure or small differential reading. |
| 0.2 bar | 5.906 inHg | Useful vacuum cross-check. |
| 0.5 bar | 14.765 inHg | Half bar is not half atmosphere. |
| 0.75 bar | 22.147 inHg | Below standard atmosphere. |
| 1.0 bar | 29.530 inHg | Exact bar anchor. |
| 1.01325 bar | 29.921 inHg | Standard atmosphere. |
| 1.2 bar | 35.436 inHg | Above atmospheric pressure. |
| 1.5 bar | 44.295 inHg | Light gauge-pressure equipment range. |
| 2.0 bar | 59.060 inHg | Workshop gauge comparison. |
| 3.0 bar | 88.590 inHg | Higher equipment pressure. |
| 5.0 bar | 147.650 inHg | Industrial pressure reference. |
Pressure Context Checks
Weather Pressure
Barometer and altimeter settings are normally near standard atmosphere. Values far from 29 to 31 inHg may need a unit or decimal check.
Gauge Pressure
A tyre or compressor gauge often reads pressure above local atmosphere. Do not mix that with absolute pressure without adding the reference pressure.
Vacuum Pressure
Vacuum instruments may show inches of mercury below atmosphere. That is not the same as an absolute inHg value.
Related Pressure Conversions
| Conversion | Factor | Use |
|---|---|---|
| bar to Pa | multiply by 100,000 | Base SI pressure calculation. |
| bar to kPa | multiply by 100 | Engineering specifications. |
| bar to hPa | multiply by 1,000 | Weather and aviation pressure. |
| bar to psi | multiply by 14.5038 | Tyres, pumps and US equipment. |
| bar to mmHg | multiply by 750.062 | Laboratory and pressure tables. |
| bar to atm | divide by 1.01325 | Atmosphere comparison. |
| inHg to hPa | multiply by 33.86389 | Altimeter and weather conversion. |
| inHg to psi | multiply by 0.491154 | Vacuum and workshop gauges. |
| inHg to mmHg | multiply by 25.4 | Mercury column units. |
| 29.9213 inHg to hPa | 1013.25 hPa | Standard atmosphere check. |
FAQs
How many inches of mercury are in one bar?
One bar is 29.5299801647 inHg using the conventional inch of mercury value of 3,386.389 pascals. For most display work, 1 bar = 29.530 inHg is a practical rounded value.
Is 1 bar the same as 29.92 inHg?
No. 29.92 inHg is the rounded standard atmosphere value, equal to about 1.01325 bar. One bar is slightly lower, at about 29.53 inHg. The two are close enough to cause mistakes if the distinction is ignored.
Does the converter use inches of mercury at 0 C?
It uses the conventional inHg factor listed by NIST: 1 inHg = 3,386.389 Pa. Historical mercury column values can depend on temperature and gravity definitions, but this conventional factor is the practical engineering and weather conversion used here.
Can I use this for aircraft altimeter settings?
It can convert the pressure number, but it does not replace aviation procedures, local altimeter settings or certified instruments. If the value is for flight planning or operation, use approved aviation sources and keep the pressure setting in the format required by that procedure.
Why are hPa and mbar the same number?
One hectopascal is 100 pascals. One millibar is also 100 pascals, so weather reports often use hPa and older material may use mbar with the same numerical value. One bar is 1,000 hPa or 1,000 mbar.
Can I convert vacuum inches of mercury with this page?
Yes for unit size, but read the instrument label carefully. A vacuum gauge may show inches below atmospheric pressure, while an absolute pressure reading uses zero pressure as its reference. The same number can mean different physical conditions.
Sources
- National Institute of Standards and Technology. (n.d.). Pressure And Gas Flow Unit Conversions. NIST. https://www.nist.gov/pml/owm/metric-si/unit-conversion/pressure-and-gas-flow-unit-conversions
- National Institute of Standards and Technology. (2008). Guide For The Use Of The International System Of Units (SI), Appendix B. NIST. https://www.nist.gov/physical-measurement-laboratory/nist-guide-si-appendix-b8
- Bureau International des Poids et Mesures. (2019). The International System of Units (SI), 9th edition. BIPM. https://www.bipm.org/en/publications/si-brochure
- National Oceanic and Atmospheric Administration. (n.d.). Air Pressure. NOAA. https://www.noaa.gov/jetstream/atmosphere/air-pressure