It is an inverse lookup. But if you don't know what linear interpolation is, then it makes me scratch my head.
Over here this stuff is learned in primary school. It's on the curriculum, as it's used in basic geometry, you take two points, determine the linear function and then solve f(x) = y for the x that you need.

it's very true.  unless you have some specific reason to study math as a major, like becoming a math professor, or go into engineering or something like that, then you can pretty much skip the subject entirely!!!

well.. that's exactly why I haven't used the spreadsheet yet

Isn't that a little severe? Or are you just joking?
 I've been able to do everything else.
Just the kfmirl last row limits my maximum boost.

Heck i been literally running a stage 2+ tune done all by myself, with a full wideband conversion. nonstock maf, nonstock injectors, 4bar fpr upgrade, 19-21lbs of boost. advanced timing.  really good mafg readings.
And the car runs smooth on it. I've even done two track days on the engine with zero issues.

It's simply going well enough that I want to try the 5120hack out. But i'll need to go higher than stock kfmirl.