The calculator is based on static measurements for wrist size etc.
The problem is that wrist size (tendon and bone size and strength) is not static, but adapts under the right conditions.
An inch of wrist(etc) size can change the calculation’s outcome big time… The entire “logic” behind the calculator is thus (even when not counting the numerous other issues such as differences in competition shape and muscle-loss from back in the day vs today, credibility of the measurements obtained etc) fatally flawed.
This does not only affect drug-users and young people… Otherwise, every drug-free guy over 30 would be unable to ever recover from a broken bone, or ever bench more than ~250 or some such without tearing something instantly.
The calculator cannot predict any kind of future potential.
It can at most tell you how much mass you should have at a given, static wrist(etc)-size according to the data it is based on (i.e. scaled against the people whose supposed measurements Mr. Butt used to create this thing).
This is the reason for why so many people get roughly (plus minus) their current stats (with some flukes here or there due to differences in training age, strength, diet, training style, whether they train a muscle and have made the right amount of progress on the given exercises, muscle-shape and what have you… All compared to the group Casey used, or made up or whatever)…
If you’ve been training for 20 years and have never had it in you to truly lift heavy and progressively across the board (hint: If you want 20+ inch arms, it may help to be curling the 90’s or 100’s among other things… What, you can’t believe somebody could possibly do that? Well idiot, find a goddamn way to get there instead of making excuses.), then of course you’ll be convinced that you’re at some kind of limit.
You are indeed… The limit imposed upon you by your current diet first and foremost, then training style… And possibly hormone levels (helps if you aren’t 50 at the time you’re beginning your journey drug-free).
Please note that Mr. Butt is now selling the whole thing as an e-book for money.
Also note the comments about how people who have reached the limit can use that information to focus on something else now, as there is no reason to try and achieve more (it is impossible, after all).
So he tries to convince you of your limits first, and then wants to prevent you from ever finding out the truth by making sure you make no real attempt to get past them.
This entire thing is ultimately a trick similar to the ones used in commercials and by just about everyone trying to sell you something dodgy… Or by various quasi-religious gurus etc…
Fool: “Okay, I don’t think this actually works, but tell me my fortune anyway.”
Fortune Teller: “I see dark times ahead for you, but also good times.”
Fool (2 weeks later): “Oh wow Mr. Fortune Teller, you were totally right! On the one hand, I cut myself with a knife, but on the other hand, my favorite series is being aired again! Please tell me my future again, oh wise one!”
Fortune Teller: “I see even darker times (potentially involving a machete or chainsaw) ahead, but only if you do not pay me. Er. Cash or credit card?”