Atmospheric Pressure to Altitude for High Altitude Ballooning

We are frequently asked about how to convert between atmospheric pressure and altitude for high altitude balloon flights. Our Doongara balloon cut-down device has a pressure sensor that can be configured to cut a line at a specific pressure. But what if you have a specific altitude in mind? Is there a way to correlate the two?

Basic Atmospheric Pressure to Altitude Calculators

The easiest method to convert altitude to atmospheric pressure is to use the barometric equation. Use it to solve for an approximate pressure at the desired altitude. This equation assumes that the Earth’s atmosphere is stable and excludes weather and solar heating. This method is useful for most high altitude balloon flights that only need an approximate correlation between atmospheric pressure and altitude.

Barometric Equation for converting Atmospheric Pressure to Altitude

ParameterDescriptionValue
p0sea level standard atmospheric pressure101325 Pa
T0sea level standard temperature288.15 K
gEarth-surface gravitational acceleration9.80665 m/s2
Mmolar mass of dry air0.0289644 kg/mol
R0universal gas constant8.31447 J/(mol•K)

A number of websites provide easy-to-use calculators for solving this equation, such as this one. Below is a table of results for quick reference.

feetmetersmbar
1000003048010.9
950002895613.7
900002743217.3
850002590821.8
800002438427.6
750002286035.0
700002133644.4
650001981256.4
600001828871.7
550001676491.2
5000015240116.0
4500013716147.5
4000012192187.5
3500010668238.4
300009144300.9
250007620376.0
200006096465.6
150004572571.8
100003048696.8
50001524843.1

Advanced Atmospheric Pressure to Altitude Calculators

The barometric equation’s accuracy can be improved if you know the current atmospheric conditions at your location (specifically p0). Some of the website based calculators can utilize this information such as this one.

To give a sense of local pressure variations, according to Wikipedia the most extreme sea level atmospheric pressures ever recorded are currently 870 and 1083 mBar.

Recent Atmospheric Pressure to Altitude Measurements

The most accurate method for converting between atmospheric pressure and altitude is to use recent local sounding balloon measurements. Here in the United States the weather service launches these sounding balloons twice a day from a variety of locations and posts the data online. Each flight continuously measures both pressure and GPS altitude as it ascends.

We normally use this site and display the data in “Table:List” format. For example, to find the pressure at 30,000m (using the results below) interpolate between the two closest measurements ( 11.1mBar @ 29915m and 10.5mBar @ 30269m) to get approximately 10.8mBar. The closer this launch was to your launch, both temporally and in proximity, the more accurate the results will be.

-----------------------------------------------------------------------------
   PRES   HGHT   TEMP   DWPT   RELH   MIXR   DRCT   SKNT   THTA   THTE   THTV
    hPa     m      C      C      %    g/kg    deg   knot     K      K      K 
-----------------------------------------------------------------------------
 1025.0     61   10.2    5.6     73   5.59    215      6  281.4  297.0  282.3
 1021.0     93    9.4    3.4     66   4.81    217      6  280.9  294.4  281.7
 1000.0    265    7.4    2.8     73   4.70    230      8  280.6  293.8  281.4

• • •

   15.6  27737  -56.3                         140     18  711.3         711.3
   14.9  28042  -57.2                         160     13  718.2         718.2
   14.2  28347  -58.1                         168      7  725.2         725.2
   13.5  28651  -56.5                         175      2  740.8         740.8
   13.0  28905  -55.1                         166      3  754.1         754.1
   11.1  29915  -53.9                         130      8  793.3         793.3
   10.5  30269  -55.3                         118     10  800.8         800.8
   10.2  30480  -55.2                         110     11  808.9         808.9
   10.0  30580  -55.1                         105      9  812.8         812.8

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