Alexander Fufaev
My name is Alexander FufaeV and here I write about:

How Does a Barometer Work?

Important Formula

Formula: Barometric Formula
What do the formula symbols mean?


Air pressure (or the pressure of another fluid) at height \(h\) above the sea surface. According to this barometric formula, air pressure decreases exponentially with height.

Pressure at the bottom

Air pressure at sea level \(h = 0\).

Scale height

Scale height is a constant that depends, for example, on the temperature of the air and the gravitational acceleration. The scale height is approximately \(H=8\,\mathrm{km}\) on Earth.


Height measured from the sea surface.
Pressure-Height Graph of a Fluid (Air)

A simple barometer works by using the barometer formula, which relates the height \(h\) above the ground to the air pressure \( \mathit{\Pi} \) prevailing at that height:

Exponential decrease of pressure with height.

Here \( H ~=~ 8005 \, \mathrm{m} \) and the mean air pressure at sea level is \(\mathit{\Pi}_0 = 101 \, \mathrm{kPa} = 1 \, \mathrm{bar} \). The formula states that the air pressure decreases exponentially with increasing height \( h \).

So an barometer measures the air pressure \( \mathit{\Pi} \) and calculates from it the height at which this air pressure prevails: