Bletchleyite
Veteran Member
Using someone's "standing" measurements isn't the correct thing to do, even for a mildly overweight person, because people "spread out" when they sit down due to increased pressure on hips etc. There will be a cross over point at which this is more important than shoulder width and I'm not sure where but I think it'll be before obesity, possibly even before being overweight.
Let's get the tape measure out

My shoulders are roughly 55cm wide, my backside and upper thighs are 50cm wide seated (which means I fit within a typical 45cm seat base width as long as there's an armrest spacer and window side spacer as that gives you that 50cm...just!) And I am rugby sort of build and definitely fat. (Obese by BMI, but BMI doesn't work very well for very muscular builds so I'm probably really just overweight). However my shoulders do overhang slightly, usually I mitigate this by leaning into the window space which means I don't like windowless "window" seats

I agree there will be a point, but I think for men shoulder width is more of a thing. I'm definitely not "V shaped", but a lot of men are. Bashing shoulders or having to lean sideways I find much more common than legs touching.
Women will generally be wider at seat level than shoulders, but women are generally smaller anyway. Talking of 3+2, that's one reason why male-female-male or female-male-female tends to work better than three of each on the 3 side!

Not saying there aren't men wider at the backside than the shoulders while seated, but I don't think it's likely to be very many of the population. Women, certainly.
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