# Pressure units

• Question
• Updated 6 years ago
In the API you return pressure in "mb" and "in". What do these units stand for?
In Wunderground iOS pressure appears as "hPa". What does this unit stand for?
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Posted 6 years ago

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mb = millibars

in = inches

hPa = hectopascals
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inches is NOT a pressure unit !

You need to precise inches of what and what ref temperature.

For example, look at :
http://www.engineeringtoolbox.com/pre...
1 Pa (N/m2) = 0.0002953 Inch of mercury (0 C)
1 Pa (N/m2) = 0.0002961 Inch of mercury (15.56 C)

http://www.convertunits.com/from/pasc...
1 pascal is equal to 0.000295299830714 inches of mercury. (0°C)

http://www.aqua-calc.com/convert/pres...
0.0002952998751 × PPa = PinHg

http://en.wikipedia.org/wiki/Inch_of_...
1 inHg = 3386.389 Pa at 0 °C. ==> 0,000295299801647123
1 inHg60 °F = 3376.85 Pa (15.6°C) ==> 0,000296133971008484

Which one are you using ?

Tim Roche, Official Rep

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