Ozone Units
The Dobson Unit (DU) is the most common unit for measuring ozone concentration. One Dobson Unit is the number of molecules of ozone that would be required to create a layer of pure ozone 0.01 millimeters thick at a temperature of 0 degrees Celsius (0°C) and a pressure of 1 atmosphere.
Over the Earth’s surface, the ozone layer’s average thickness is about 300 Dobson Units or a layer that is 3 millimeters thick (or about thickness of two stacked pennies).