About Inch of Mercury and Millibar Conversions

Inches of mercury (inHg) and millibars (mbar) are both units used to measure atmospheric pressure. Inches of mercury is commonly used in aviation and meteorology in the United States, while millibars are used internationally and in scientific contexts.

Conversion Formula

The exact conversion factor between inches of mercury and millibars is:

1 inHg = 33.8639 mbar
1 mbar = 0.02953 inHg

Practical Examples

Standard sea level pressure is 29.92 inHg or 1013.25 mbar
Aviation altimeters use inHg for pressure setting in the US
Weather maps typically show pressure in mbar or hPa (1 hPa = 1 mbar)

Reference Table

inHg	mbar
28.00	948.19
29.00	982.05
29.92	1013.25
30.00	1015.92
31.00	1049.78

Important Notes

The conversion factor is exact and based on NIST standards
Pressure measurements may be reported in different units regionally
Aviation uses inHg for altimeter settings in the US, but other countries may use hPa

Frequently Asked Questions

Why are there different pressure units?

Different fields and regions have historical preferences. Aviation in the US uses inHg, while meteorology internationally uses millibars or hectopascals.

Is the conversion exact?

Yes, 1 inch of mercury is exactly 33.8639 millibars based on the definition of mercury density and gravitational acceleration.

What is the difference between mbar and hPa?

Millibars and hectopascals are equivalent units: 1 mbar = 1 hPa. Both represent 100 pascals of pressure.

Inch of Mercury to Millibar Converter

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Common Pressure Conversions

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Inch of Mercury to Millibar Converter

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