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InHg to hPa Converter

Enter an altimeter setting in inHg, hPa, mmHg or kPa to see it in the other units and how a change of setting moves the indicated altitude.

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The inHg to hPa converter takes a pressure in inches of mercury, hectopascals, millimeters of mercury or kilopascals and gives the same pressure in the other three units. Enter the pressure, choose the unit it is written in, and the result shows the converted value to three decimals, for example 29.92 inHg as 1013.21 hPa.

Add an indicated altitude and a new altimeter setting to see the altitude effect. The result shows how far the indicated altitude moves for each 1 hPa or 0.01 inHg change of setting, next to the 1,000 ft per inHg rule from the FAA handbook. The altitude effect appears between about 25.1 and 32.0 inHg (850 to 1,085 hPa). Outside that range the conversion still works, but the altitude effect is not shown. This is a planning aid, so check the aircraft flight manual for your aircraft.

Inhg to hpa example

How to use the inHg to hPa converter

  1. Type the pressure into Pressure to convert, for example 29.92 for a U.S. altimeter setting.
  2. Set From to the unit the pressure is written in: inHg, hPa (mb), mmHg or kPa.
  3. Set To to the unit you need. The Converted value shows the result to three decimals, and the result list also gives the pressure in all four units.
  4. Open More options to set the Indicated altitude for the altitude effect (in feet, default 3,000). To compare two settings, enter a New altimeter setting (optional) in the same unit as the pressure above.
  5. Read Pressure altitude at sea level with this setting and the altitude change per unit of setting. With a new setting, compare Indicated altitude change, new setting minus old with the 1,000 ft per inHg rule and Rule minus exact value.
  6. Use the presets to load 29.92 inHg, Q1013 to inHg, a setting that falls from 30.12 to 29.62, or 760 mmHg. Copy link keeps your inputs, Print / save result makes a sheet, and Reset starts over.
  7. Open How it was calculated to read how the result was worked out.

The table under the result lists 28.00 to 31.00 inHg in 0.10 steps, plus 29.92, in inHg, hPa, mmHg and kPa, with the pressure altitude at sea level for each setting. Use it when you only need a quick look-up and no calculation. Values outside the altimeter range of about 25.1 to 32.0 inHg still convert, but the altitude lines are left out.

How do you convert inHg to hPa?

Multiply the inches of mercury by 33.86389 to get hectopascals, because one inHg equals 33.86389 hPa. Going the other way, divide the hPa value by 33.86389, or multiply it by 0.02953. For a U.S. setting of 29.92 inHg, that gives 29.92 x 33.86389 = 1013.21 hPa.

The factor comes from NIST SP 811, which gives the conventional inch of mercury as 3,386.389 Pa, the value altimeter settings use. One hPa is one mbar, or 100 Pa, and one mmHg is 133.322387415 Pa.

What is 29.92 inHg in hPa?

29.92 inHg is 1013.21 hPa. The U.S. setting of 29.92 is the standard sea-level pressure of 29.9213 inHg rounded, and that rounded value converts to 1013.21 hPa, not the standard 1013.25 hPa. Enter 29.92 with From set to inHg and To set to hPa (mb) to see it in the Converted value.

Standard sea-level pressure is 101,325 Pa, which is 1013.25 hPa, 29.9213 inHg and 760 mmHg. Other settings the tool converts:

  • 28.00 inHg = 948.19 hPa
  • 30.00 inHg = 1015.92 hPa
  • 30.12 inHg = 1019.98 hPa
  • 31.00 inHg = 1049.78 hPa

What is 999 hPa in inHg?

999 hPa is 29.500 inHg, or 749.3 mmHg. To get it, divide 999 by 33.86389, which gives the same result as multiplying by 0.02953. Enter 999 in Pressure to convert, set From to hPa (mb) and To to inHg, and the Converted value reads 29.500. For nearby values, 1000 hPa is 29.530 inHg and 1020 hPa is 30.121 inHg.

How does a change in altimeter setting change the indicated altitude?

Raising the setting by 1 hPa lifts the indicated altitude by 27.3 ft at sea level, and 0.01 inHg is worth 9.2 ft at the same altitude. These figures come from the standard atmosphere model, not from the 1,000 ft per inHg rule.

The rule is an approximation of the standard pressure lapse, which the FAA handbook describes as about 1 inHg per 1,000 ft of altitude gain up to 10,000 ft. The exact figure shifts with altitude: at 3,000 ft one hPa is worth 26.7 ft and 0.01 inHg is 9.1 ft, while at 10,000 ft they are 25.4 ft and 8.6 ft. Take a setting that falls from 30.12 to 29.62 inHg with the indicated altitude at 3,000 ft. The exact change is -454 ft, while the rule gives -500 ft, a 46 ft difference.

Sources

NIST SP 811 Appendix B.8 conversion factors (inch of mercury, millibar, millimeter of mercury); U.S. Standard Atmosphere 1976 (NASA-TM-X-74335) for sea-level pressure and the pressure law; FAA-H-8083-25B Pilot’s Handbook of Aeronautical Knowledge (2016), chapters 8 and 11; FAA Aeronautical Information Manual chapter 7 section 1 (METAR altimeter group). Checked October 2026.

Questions from readers

Is hPa the same as mb?

Yes. One hPa equals one millibar (mb), so the hPa (mb) unit gives the same value as a millibar reading.

Why is 29.92 inHg 1013.21 and not 1013.25 hPa?

Because 29.92 is the standard pressure of 29.9213 inHg rounded to two decimals. The exact standard value, 1013.25 hPa, converts back to 29.9213 inHg.

How do I convert hectopascals to barometric pressure (inHg)?

Divide the hPa value by 33.86389. For example, 1013 hPa divided by 33.86389 gives 29.914 inHg.

What does Q1013 or A2992 mean in a METAR?

Q1013 is the altimeter setting in hectopascals. A2992 is the same kind of setting in inches of mercury: A followed by inches and hundredths, so A2992 means 29.92 inHg.

Which countries use hPa and which inHg?

The tool does not list countries. The FAA Aeronautical Information Manual says that in the U.S. the altimeter group is A followed by inches and hundredths, and that a Q group gives hectopascals. Check the group in the METAR or ATIS you are given.

How accurate is the 1,000 ft per inHg rule?

The rule is an approximation of the standard pressure lapse, and the gap grows with the size of the change. At 3,000 ft indicated, a fall from 30.12 to 29.62 inHg gives -454 ft exact against -500 ft by the rule, a 46 ft difference.

Do I need to convert for the aircraft’s altimeter?

Many altimeters have both scales, so set the unit the controller gives you. The converter helps you check the numbers, but the altimeter scale in your aircraft decides what you set.