Quote Originally Posted by aps2012 View Post
Whether a jacket fits you depends on where it falls on your body, not on what number or letter is inside on the label. I prefer a jacket that properly covers one's back side and don't really like the cropped look of the last 5 or so years. But perhaps we're moving back a little longer which is why the guidance on S, R, and L, seems to be changing? I wouldn't trust JCrew or Suit Supply not to change the "proper" fit based on changing fashions.
This is true, but generally speaking if your proportions are anywhere near average, knowing your height should get you pretty close to determining whether you are a short, regular, or long. The guidelines are it should just cover your backside - basically ending at the crease where your buttocks meet the upper thigh. For most guys, that is where the first knuckle of the thumb falls (the one closest to the tip of the thumb) so that is an alternate guide. I think this standard still applies whether things trend more boxy/full cut or tailored. Look at Humphrey Bogart - that was a full cut era but the rule still applies if you look at photos of him in a suit. I've had good luck with getting the right length from J Crew following their size guidance and have been buying jackets from them for over a half decade. The Ludlow fit is very tailored but not shortened beyond the norm. Some retailers did indeed go shorter though.