You can get a kestrel. Easiest as it’s all done for you. There are simple density altitude charts available or you can memorize a few easy. Numbers and always be within a couple hundred feet of actual DA. The good news is with DA, rounding to the nearest 1000 is more than acceptable so the difference between 3700 DA and using 4000 is non existent.

first and foremost standard atmosphere is 59 F 29.92 in Hg pressure and 0% humidity. So at sea level at exactly those conditions your DA equals 0 as well as your elevation. Temp has a standard lapse rate of approximately 3.5 degrees F per 1000 feet of elevation gain and a standard pressure lapse rate of 1” Hg per 1000 feet. DA increases approximately 1000’ for every 15 degrees from the standard at a given elevation.

So at for example 4000 feet, if the conditions were 45 F and 25.92 in Hg your DA and elevation would be equal (I’m ignoring the effect of humidity. It’s irrelevant for our purpose). If the temp was 60 degrees your DA would be 5000 feet.

does that make sense?

for more accurate calculations accounting for pressure changes use this

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here are the standard atmosphere numbers for the hasty method I showed above

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or just save yourself the headache and carry this

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