I am not sure if anyone here has the answer, but I'll ask anyway: When a seed bank gives the THC percentage for a strain, are they measuring the whole plant, just the flower or something else? When I make edibles, I have been using this information to calculate the potency. I only use bud and my calculation is: (milligrams of bud x THC percent x efficiency of extraction) / number portions = milligrams per portion. I do realize that this is just approximate, you would need to do a real chemical analysis to find the real number.
If you want to know the true THC% of any strain you need to send off a sample to a lab of the weed you've grown... the seed may advertise a strain at 20% but there's no saying the weed you've grown is the same %.
Good question. I gotta think if those who would benefit from higher tested strains are responsible for testing the numbers could be skewed. I've read before if you want higher numbers take a top bud a little before it's totally ripe. If you do that of course it looks good but what about all the other buds? I don't think anyone would argue they're all the same. I use my own mostly untested buds and concentrates. I try to be conservative in the numbers I use. I grow mostly sativa hybrids that can have total thc in the 20+% range, but use 15-18% as averages when figuring doses. And then use 80% as an extraction rate for buds when extracting in oil/butter. For rosin I use 750mg/g. I came up with that number because ive read thats the industry average. Sift hash at 550mg/g. My winterized feco ive had tested at 860mg/g, so I use 800-850. And I make it clear to anyone eating my edibles, these are only estimates.
I use pretty much the same: 20% THC, 80% efficiency for a rough calculation. I make a few different types of edibles, and capsules. They all have a different portions number but I start them out the same way: create an alcohol tincture then put it in a still to remove the alcohol. I then start everything with the resulting oil. I grow a variety of strains and clone the better plants so the breeder's THC number is of interest to me.