I am trying to find out the pressure at a given altitude but have been disappointed to find the following equation does not work at all: (h = height in meters)

![enter image description here](https://i.stack.imgur.com/ujJjV.png)

Where 

* sea level standard atmospheric pressure p0 = 101325 Pa
* sea level standard temperature T0 = 288.15 K
* Earth-surface gravitational acceleration g = 9.80665 m/s2.
* temperature lapse rate L = 0.0065 K/m
* universal gas constant R = 8.31447 J/(mol·K)
* molar mass of dry air M = 0.0289644 kg/mol

( from [Wikipedia](http://en.wikipedia.org/wiki/Density_of_air#Altitude) )

Upon completion of the equation, which I think spits out Pascal values, they don't match what a pressure would realistically look like at that altitude (comparing the output value to one from Wolfram). Any idea what the issue with this equation is?

EDIT: inaccuracy alone isn't the problem, it's not giving the right values for anything. I saw a value of 101800 or so for an altitude of 800ft, which is completely wrong, and then the output starts turning into negatives around 100,000ft. I do need something to work at that height, perhaps this isn't the equation for me?