This calculator is derived from Wikipedia's Density_of_air article.
Enter the height and click on the Calculate button to see the temperature, pressure and density of air at that altitude.
Caveat: the Titan example uses back of the envelope estimates for the molecular weight of the nitrogen-methane atmosphere, and wild guesses for the lapse rate and tropopause altitude. This page including the javascript is Copyright 2005 User:Wikibob and placed in the Public domain.