Atmospheric Pressure vs Altitude

Pressure At Sea Level Is About 100,000 pascals Or 100 kilopascals Or 1 bar Or 1000 millibars.
(Or 29.61 inch mercury [inHg] @ 59°F/288.15 kelvin).

For high altitudes within the troposphere, the following equation (the
Barometric formula) relates atmospheric pressure p to altitude h where the constant parameters are as described below:

Parameter	Description	Value
p0	sea level standard atmospheric pressure	101325 Pa
L	temperature lapse rate, = g/cp for dry air	0.0065 K/m
cp	constant pressure specific heat	~ 1007 J
T0	sea level standard temperature	288.15 K
g	Earth-surface gravitational acceleration	9.80665 m/s2
M	molar mass of dry air	0.0289644 kg/mol
R	universal gas constant	8.31447 J/(mol•K)