I take all my clothing tips from Wanny Di Filippo and have never had any problems…. https://www.pinterest.ca/TinYue/wanny-di-filippo/
In my experience, between manufacturers, men’s pant sizes might vary by as much as an inch, but usually not that much. You still have to try them on, because shape matters in ways that aren’t described by just two numbers, but you don’t usually have to try on very many.
For shirts, I have one that’s labeled as “M” that fits great, one labeled “XL” that’s a little bit on the baggy side but still basically fits, and all the rest that are sized in the “SML” scheme are L and fit fine. When I see a shirt in a store that’s labeled L, I can generally be pretty confident it’ll fit even without trying it on. Dress shirts are sometimes sized in neck-and-sleeve, and those are also usually pretty consistent, and have a little more tolerance than pants.
One trick you can use for pants, in situations where you won’t be able to try them on (for instance, at the church rummage sale) is to close the fly and then fit your forearm into them. Your forearm-and-fist is probably fairly close in circumference to your waist. Of course, you want to calibrate this at home with a pair of pants that you know fits well before you go: You might need to make it a half-fist, or bend your wrist, or the like, but then just remember how you had your hand.
Hmm, maybe I’ll just stop dressing up. A pair of Levi’s 550 (Relaxed FIt) and a large t-shirt and I’m good to go.
Okay, that’s it. When people ask Future Me how I lost “all that weight!” and got back to my younger pants size, I’ll say "Well, this guy I know used the phrase ‘since I became a doughboy’ and I said “Oh, noooo, that’s going to be meeee… I don’t want to be a weird shape…”
Hey, whatever helps.
I do try not to kid myself. My shape is actually (and sadly) not that weird statistically, I see a lot of men in the same ballpark – and I never see them dressed up. I suspect I know why.
With the internet, big and tall guys are living in a golden age of clothes buying. No more buying extra big shirts just so the sleeves are long enough. No more sweatshirts where the shoulder seam is half way down my upper arm.
I try them on. They are just so unlikely to fit otherwise that it’s not worth the effort; I loathe sending things back to the shop - it’s as much effort as going to the shop. I bought zero clothes during lockdown.
The worst thing is that I am fairly slim, but not tiny, have curves, because I’m female, and the upper curves roughly match the lower ones. It should be easy for me to find clothes that fit me. Trousers do tend to be the right length, except even then the knees often start somewhere closer to my ankles than they should. What humans are they measuring these things against?
But I’ve held jeans up against me where the waistband looked right or even a little large, and the legs didn’t get past my not-large-at-all thighs. I’ve tried on dresses that seemed to think boobs start around belly-button height and literally showed every single bit of my bra.
So basically I either buy from trusted brands, try stuff on, or buy something really stretchy. And I don’t buy clothes very often, then wear them a lot.