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Air Density and Specific Weight Equations and Calculator

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 Engineering Physics

Air Density and Specific Weight Table, Equations and Calculator:

The density of air, ρ (Greek: rho) (air density), is the mass per unit volume of Earth's atmosphere. Air density, like air pressure, decreases with increasing altitude. It also changes with variation in temperature or humidity. At sea level and at 15 °C, air has a density of approximately 1.225 kg/m3 (0.001225 g/cm3, 0.0023769 slug/ft3, 0.0765 lbm/ft3) according to ISA (International Standard Atmosphere).

Temperature F = 
Relative Humidity % RH = 
Barometer B (in) =
Altitude (ft Above Sea Level) A =
Equation
Altitude (meters) = A*12*2.54/100
Temperature Degrees C = ((F-32)*5/9)
Temperature kelvin k = C+273
Barometer  (mbar) = B/(29.92/1013)
Barometer (mb) = 1013*EXP(-B7/7000)
Barometer (in) = mb*(29.92/1013)
Ms (g/kg) = 3.884266*10^((7.5*k)/(237.7+C))
M (g/kg) = Ms*RH/100
Tvc = ((1+1.609*M)/(1+M))*k
Es (saturation pressure mb) = 6.11*10^(7.5*C/(237.7+k))
E (Vapor Ressure mb) = (RH*Es)/100
Tdc = (-430.22+237.7*LN(B17))/(-LN(B17)+19.08)
Tdf = Tdc*9/5+32
Equation: D=P/(T*R) =  Std Density (100)
Temp, Altitude, Pressure, and Humidity
Barometer (alt-station) as = mb*EXP(-B7/7000)
D (air density) (kg/m3) ad = (as*100)/(B9*287)
Corrected Density =
D (virt air density) (kg/m3) vad = (as*100)/((B15+273)*287)
Corrected Density =

Specific weight and density of air at standard atmospheric pressure - Imperial Units:

Temperature
°F
Density
slugs/ft3
Specific Weight
lb/ft3
-40
.002939
.09456
-20
.002805
.09026
0
.002683
.08633
10
.002626
.08449
20
.002571
.08273
30
.002519
.08104
40
.002469
.07942
50
.002420
.07786
60
.002373
.07636
70
.002329
.07492
80
.002286
.07353
90
.002244
.07219
100
.002204
.07090
120
.002128
.06846
140
.002057
.06617
160
.001990
.06404
180
.001928
.06204
200
.001870
.06016
250
.001756
.05598
300
.001624
.05224
400
.001435
.04616
500
.001285
.04135
750
.001020
.03280
1,000
.000845
.02717
1,500
.000629
.02024

Specific weight and density of air at standard atmospheric pressure - SI Units:

Temperature
°C
Density
kg/m3
Specific Weight
N/m3
-40
1.514
14.85
-20
1.395
13.68
0
1.293
12.67
5
1.269
12.45
10
1.247
12.23
15
1.225
12.01
20
1.204
11.81
25
1.184
11.61
30
1.165
11.43
40
1.127
11.05
50
1.109
10.88
60
1.060
10.40
70
1.029
10.09
80
0.9996
9.803
90
0.9721
9.533
100
0.9461
9.278
200
0.7461
7.317
300
0.6159
6.040
400
0.5243
5.142
500
0.4565
4.477
1000
0.2772
2.719

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