Temperature 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 temperature (only) expansion and contraction differences. The metal housing of the barometer and the mercury both expand as the temperature increases. However, they expand at different rates. The barometer is calibrated for 0 degrees C (32 degrees F). For different temperatures a correction must be applied to compensate for the different expansions of the housing and the mercury. For temperatures greater than 0 degrees C, the correction should be added to the observed height; for temperatures less than 0 degrees C, the very minor correction should be subtracted. Contraction differences are extremely small and almost negligible. The default values are typical for the general lower desert area of Southern California. To use the calculator, enter the temperature and the known and observed barometer reading, in any of the designated values, then click on Calculate. Results are returned in both inches of mercury and millibars. There is also a temperature correction chart 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 altitude correction only, for gravity (latitude) correction only, for temperature and altitude correction and for gravity, altitude, and temperature correction.


Unit
Value
Required Data Entry
Air Temperature Degrees
 °C  °F
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 Chart For Relative Expansion Of Mercury And Brass Scale To 32░F Standard
Temp1
°F
Observed reading of the barometer, in inches
25 25.5 26 26.5 27 27.5 28 28.5 29 29.5 30 30.5 31.0
Correction to be subtracted from observed reading
40 .026 .026 .027 .027 .028 .028 .029 .029 .030 .030 .031 .031 .032
42 .030 .031 .032 .032 .033 .033 .034 .035 .035 .036 .036 .037 .038
44 .035 .036 .036 .037 .038 .038 .039 .040 .040 .041 .041 .042 .043
46 .039 .040 .041 .042 .043 .043 .044 .045 .046 .046 .047 .048 .049
48 .044 .045 .046 .047 .047 .048 .049 .050 .051 .052 .053 .054 .054
50 .048 .048 .050 .051 .052 .053 .054 .055 .056 .057 .058 .059 .060
52 .053 .054 .055 .056 .057 .058 .059 .060 .061 .062 .064 .065 .066
54 .057 .059 .060 .061 .062 .063 .064 .066 .067 .068 .069 .070 .071
56 .062 .063 .064 .066 .067 .068 .069 .071 .072 .073 .074 .076 .077
58 .066 .068 .069 .070 .072 .073 .074 .076 .077 .078 .080 .081 .082
60 .071 .072 .074 .075 .077 .078 .080 .081 .082 .084 .085 .087 .088
62 .076 .077 .079 .080 .082 .083 .085 .086 .088 .089 .091 .092 .094
64 .080 .082 .083 .085 .086 .088 .090 .091 .093 .095 .096 .098 .099
66 .085 .086 .088 .090 .091 .093 .095 .096 .098 .100 .101 .103 .105
68 .089 .091 .093 .094 .096 .098 .100 .102 .103 .105 .107 .109 .110
70 .094 .095 .097 .099 .101 .103 .105 .107 .109 .110 .112 .114 .116
71 .096 .098 .100 .102 .103 .105 .107 .109 .111 .113 .115 .117 .119
72 .098 .100 .102 .104 .106 .108 .110 .112 .114 .116 .118 .120 .122
73 .100 .102 .104 .106 .108 .110 .112 .115 .116 .118 .120 .122 .124
74 .103 .105 .107 .109 .111 .113 .115 .117 .119 .121 .123 .125 .127
75 .105 .107 .109 .111 .113 .115 .117 .119 .122 .124 .126 .128 .130
76 .107 .109 .111 .113 .116 .118 .120 .122 .124 .126 .128 .131 .133
77 .109 .112 .114 .116 .118 .120 .122 .125 .127 .129 .131 .133 .136
78 .112 .114 .116 .118 .120 .123 .125 .127 .129 .132 .134 .136 .138
79 .114 .116 .118 .121 .123 .125 .127 .130 .132 .134 .137 .139 .141
80 .116 .118 .121 .123 .125 .128 .130 .132 .135 .137 .139 .142 .144
81 .118 .121 .123 .125 .128 .130 .132 .135 .137 .140 .142 .144 .147
82 .121 .123 .125 .128 .130 .133 .135 .137 .140 .142 .145 .147 .149
83 .123 .125 .128 .130 .133 .135 .138 .140 .142 .145 .147 .150 .152
84 .125 .128 .130 .133 .135 .138 .140 .143 .145 .148 .150 .153 .155
85 .127 .130 .132 .135 .137 .140 .143 .145 .148 .150 .153 .155 .158
86 .130 .132 .135 .137 .140 .142 .145 .148 .150 .153 .155 .158 .161
87 .132 .134 .137 .140 .142 .145 .148 .150 .153 .155 .158 .161 .163
88 .134 .137 .139 .142 .145 .147 .150 .153 .155 .158 .161 .163 .166
89 .136 .139 .142 .144 .147 .150 .153 .155 .158 .161 .164 .166 .169
90 .138 .141 .144 .147 .150 .152 .155 .158 .161 .163 .166 .169 .172
92 .143 .146 .149 .152 .154 .157 .160 .163 .166 .169 .172 .174 .177
94 .147 .150 .153 .156 .159 .162 .165 .168 .171 .174 .177 .180 .183
96 .152 .155 .158 .161 .164 .167 .170 .173 .176 179 .182 .185 .188
98 .156 .160 .163 .166 .169 .172 .175 .178 .181 .185 .188 .191 .194
100 .161 .164 .167 .171 .174 .177 .180 .183 .187 .190 .193 .196 .200

  Note1: Temperature of the column of mercury in degrees Fahrenheit.


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