First, enter your Elevation in metres or feet (a minus figure if you're below sea level). Next enter the Barometric Pressure at your nearest Observation Location in millibars or inches of mercury (Hg) If you don't have this information use the default values and the results will be almost the same. Then click on Calculate and the results will appear both in millibars and inches of mercury (Hg). The bottom row of  figures is the most useful.


  Metric Imperial
Elevation M Ft
Barometric  Pressure (leave at default if you don't know)
Millibars inHg
Amount of Reduction in Vacuum Reading
(Rounded off)
Your Maximum Theoretical Vacuum
Your Maximum Theoretical Vacuum (Rounded off)

If you don't know your elevation, search for your city in Wikipedia. Look in the right hand column and it will show the elevation just above the population data.

One note...just because your maximum theoretical vacuum is lower than someone at sea level, this does not mean your stabilizing results will be less effective!  At higher elevations, the air is thinner so there is less air in the material to begin with.  In other words, if you are at a higher elevation, you have a head start over the person at sea level!