Many people know that they need to set their domestic barometer to get it to read sea level atmospheric pressure, although the barometer itself is not at sea level. The Department frequently gets asked about this, and these brief notes explain why this adjustment is needed and how it can be carried out .
Barometers are instruments used to measure atmospheric pressure.
Divide the reading in inches of mercury by 0.0295 to convert it to a pressure in millibars. Some continental barometers are calibrated in centimetres of mercury. To convert this to a reading in millibars, first multiply the number of cm by 2.54 to get to inches of mercury, and then divide by 0.0295 as above. More information on units . Atmospheric pressure varies with height above sea level as well as with atmospheric conditions.