Gravity 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 gravity differences in different latitudes. Because the Earth is not a perfect sphere, the acceleration due to gravity depends on latitude. The radius of the earth is greater at the equator than at the poles. This means that gravity is least at the equator and greatest at the poles. Thus at smaller latitudes the mercury in the barometer tube weighs less, and will require a greater length to balance a given pressure. The barometer is calibrated for a latitude of 45 degrees. For latitudes less than 45 degrees, the correction should be subtracted from the observed height; for latitudes greater than 45 degrees the correction should be added. The default values are typical for the general lower desert area of Southern California. To use the calculator, enter the latitude and the known and observed barometer reading in either designation, then click on Calculate. Results are yielded in both inches of mercury and millibars. If you don't know the latitude, you can use our USA longitude and latitude map to get an idea of the general area. There is also a latitude correction chart below the calculator. Other pressure correction calculators are for temperature correction only, for altitude correction only, for temperature and altitude correction and for gravity, altitude, and temperature correction.


Unit
Value
Required Data Entry
Latitude degrees
Observed Barometer Reading
 Millibars  Inches Hg
   
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 Of Mercurial Barometer For Latitude In Inches Hg To Reduce To 45 Degrees Latitude
To be added to barometer readings for latitudes above 45 degrees,
or subtracted from barometer readings for latitudes below 45 degrees.
Latitude Reading of the barometer, in inches
18 19 20 21 22 23 24 25 26 27 28 29 30
0 90 0.047 0.049 0.052 0.054 0.057 0.060 0.062 0.065 0.067 0.070 0.073 0.075 0.078
5 85 .046 .048 .051 .054 .056 .059 .061 .064 .066 .069 .071 .074 .077
6 84 .046 .048 .051 .053 .056 .058 .061 .063 .066 .068 .071 .073 .076
7 83 .045 .048 .050 .053 .055 .058 .060 .063 .065 .068 .071 .073 .075
8 82 .045 .047 .050 .052 .055 .057 .060 .062 .065 .067 .070 .072 .075
9 81 .044 .047 .049 .052 .054 .057 .059 .062 .064 .067 .069 .071 .074
10 80 .044 .046 .049 .051 .054 .056 .058 .061 .063 .066 .068 .071 .073
11 79 .043 .046 .048 .050 .053 .055 .058 .060 .062 .065 .067 .070 .072
12 78 .043 .045 .047 .050 .052 .054 .057 .059 .062 .064 .066 .069 .071
13 77 .042 .044 .047 .049 .051 .054 .056 .058 .061 .063 .065 .068 .070
14 76 .041 .043 .046 .048 .050 .053 .055 .057 .059 .062 .064 .066 .069
15 75 .040 .043 .045 .047 .049 .052 .054 .056 .058 .061 .063 .065 .067
16 74 .040 .042 .044 .046 .048 .051 .053 .055 .057 .059 .061 .064 066
17 73 .039 .041 .043 .045 .047 .049 .052 .054 .056 .058 .060 .062 .064
18 72 .038 .040 .042 .044 .046 .048 .050 .052 .054 .057 .059 .061 .063
19 71 .037 .039 .041 .043 .045 .047 .049 .051 .053 .055 .057 .059 .061
20 70 .036 .038 .040 .042 .044 .046 .048 .050 .052 .054 .056 .058 .060
21 69 .035 .037 .038 .040 .042 .044 .046 .048 .050 .052 .054 .056 .058
22 68 .034 .035 .037 .039 .041 .043 .045 .047 .048 .050 .052 .054 .056
23 67 .032 .034 .036 .038 .040 .041 .043 .045 .047 .049 .050 .052 .054
24 66 .031 .033 .035 .036 .038 .040 .042 .043 .045 .047 .049 .050 .052
25 65 .030 .032 .033 .035 .037 .038 .040 .042 .043 .045 .047 .048 .050

26

64 .029 .030 .032 .033 .035 .037 .038 .040 .041 .043 .045 .046 .048

27

63 .027 .029 .030 .032 .033 .035 .037 .038 .040 .041 .043 .044 .046
28 62 .026 .028 .029 .030 .032 .033 .035 .036 .038 .039 .041 .042 .043
29 61 .025 .026 .027 .029 .030 .032 .033 .034 .036 .037 .038 .040 .041
30 60 .023 .025 .026 .027 .028 .030 .031 .032 .034 .035 .036 .038 .039
31 59 .022 .023 .024 .026 .027 .028 .029 .030 .032 .033 .034 .035 .036
32 58 .020 .022 .023 .024 .025 .026 .027 .028 .030 .031 .032 .033 .034
33 57 .019 .020 .021 .022 .023 .024 .025 .026 .027 .028 .029 .031 .032
34 56 .017 .018 .019 .020 .021 .022 .023 .024 .025 .026 .027 .028 .029
35 55 .016 .017 .018 .019 .019 .020 .021 .022 .023 .024 .025 .026 .027
36 54 .014 .015 .016 .017 .018 .018 .019 .020 .021 .022 .022 .023 .024
37 53 .013 .014 .014 .015 .016 .016 .017 .018 .019 .019 .020 .021 .021
38 52 .011 .012 .013 .013 .014 .014 .015 .016 .016 .017 .018 .018 .019
39 51 .010 .010 .011 .011 .012 .012 .013 .013 .014 .015 .015 .016 .016
40 50 .008 .009 .009 .009 .010 .010 .011 .011 .012 .012 .013 .013 .013
41 49 .006 .007 .007 .008 .008 .008 .009 .009 .009 .010 .010 .010 .011
42 48 .005 .005 .005 .006 .006 .006 .006 .007 .007 .007 .008 .008 .008
43 47 .003 .003 .004 .004 .004 .004 .004 .005 .005 .005 .005 .005 .005
44 46 .002 .002 .002 .002 .002 .002 .002 .002 .002 .002 .003 .003 .003
45 45 .000 .000 .000 .000 .000 .000 .000 .000 .000 .000 .000 .000 .000


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