Barometric Pressure (PB) is expressed in mmHg (torr).
To find out the Altitude of your City, click on the 'CITIES' button.
The formula is designed so that PB output result can't be > 760. The system doesn't allow
the input of a negative number (for altitude).
The formula presented here follows the “Equation of State” and the 1956 U.S. standard assumption.
On August 23, 1945 in document AN-T-81, the Army-Navy published the equation that relates air pressure
to altitude. That equation follows:
Pa = Po ( 1
- 6.87535*10-6Hc )5.2561
where Pa is the air pressure at
altitude Hc at a given sea level pressure Po.
Sea level pressure assumed to be 29.92 inches of mercury (760mmHg).