I just saw that, and sent a note to Josh about it. He should have an altitude field in the air density section.

Calculators like this are handy for steady-state approximation if given CdA, Crr, rho, mu, slope, etc. I think I did a calculator like that back for my old bike club back in the last millenium, based on the equations in Whitt&Wilson.

The issue here is the inverse problem: given average speed (but not power, wind, air density, slope, etc.) can you derive what CdA and Crr were? Or, even more dauntingly, can you estimate *the difference in Crr between two tires* given average speed but not power, wind, air density, etc. That's a lot harder. That's sort of like asking, can you estimate the difference in black and white mortality from COVID-19 from two different measurements of population average death rates? (This turns out to be related to a real problem I'm working on right now, which is why it's on my mind).