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Above Sea Level Barometer
Reading Correction Calculator

This calculator requires the use of Javascript enabled and capable browsers. This script determines the error in an observed barometer reading, based on elevation above (or below) sea level of the barometer and the median standard outside air temperature. The barometer is calibrated at sea level; the higher the elevation, the lower the pressure. With the barometer at elevations above sea level, the correction should be added since it is a negative value; below sea level, the value is also added but the value is positive. The default values are typical for the general lower desert area of Southern California. If you wish to show below sea level changes, just use a negative number for the appropriate elevation. To use the calculator, enter the elevation of the barometer and the known and observed barometer reading, in any of the possible designations, then click on Calculate. Actual calculations are done on inches of mercury, feet and median standard degrees F. Results are yielded in both inches of mercury and millibars (mb). The metric unit hPa (hectoPascal) is for all practical purposes, identical to the pressure unit designated as millibars; in reality, there is a very small difference, but the scientific community accepts them as the same. There is also an elevation correction chart, for a given temperature, below the calculator.

The standard value for atmospheric pressure at sea level (ATM) is equal to:

1 atm = 29.92 in Hg (inches of mercury)
1 atm = 760 mm Hg (millimeters of mercury)
1 atm = 1013.20 millibars
1 atm = 14.7 psi (pounds force per square inch)
1 atm = 1013.20 hPa (hectopascals)

To further complicate matters, there are actually 2 values for an atmosphere. The first is generally called "standard" and the other is termed as "scientific". These are based on standard atmosphere calculations. Other pressure correction calculators are for temperature correction only, for gravity (latitude) correction only, for temperature and altitude correction and for gravity, altitude, and temperature correction.

Unit
Number
Required Data Entry
Elevation Of Barometer ASL      Meters         Feet 
Observed Barometer Reading Inches Hg  Millibars 
   

Calculated Results
Actual Barometer Correction inches of mercury
Rounded Barometer Correction inches of mercury
Actual Barometer Corrected inches of mercury
Rounded Barometer Corrected inches of mercury
Actual Barometer Correction millibars
Rounded Barometer Correction millibars
Actual Barometer Corrected millibars
Rounded Barometer Corrected millibars

Correction For Elevation In Inches Hg
Per 100 Foot Difference In Elevation

To be added to barometer readings when above the datum plane or
subtracted from barometer readings when below the datum plane.

Altitude
ft
Temperature, °F
0 10 20 30 40 50 60 70 80 90
0 .122 .119 .117 .114 .112 .110 .108 .106 .104 .102
1000 .118 .115 .113 .110 .108 .106 .104 .102 .100 .098
2000 .113 .110 .108 .106 .104 .102 .100 .098 .096 .094
3000 .108 .106 .104 .102 .100 .098 .096 .094 .092 .090
4000 .104 .102 .100 .098 .096 .094 .092 .090 .088 .086
5000 .100 .098 .096 .094 .092 .090 .088 .086 .084 .082
6000 .096 .094 .092 .090 .088 .086 .084 .082 .081 .080
7000 .093 .091 .089 .087 .085 .084 .082 .080 .079 .078


Updated 8.12.11


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