Once the ground level pressure is decided on, the atmospheric pressure
*P* at other altitudes is governed by the following formula:

whereP=Pexp(-_{o}g h/H)

On Earth the scale height is 7400 metres. On other worlds it will beP= the ground level pressure_{o}

g= the surface gravity in units of Earth gravities

h= the altitude

H= the atmospheric scale height

whereH=H/_{o}M_{o}M

For breathable nitrogen-oxygen atmospheres,H= the scale height on Earth (7400 metres)_{o}

M= the mean molecular weight of Earth's atmosphere (29 atomic mass units)_{o}

M= the mean molecular weight of the planet's atmosphere

The following JavaScript form calculates the atmospheric pressure at any altitude on an alien world.