The London Lounge

I have a question about high armholes, and I'm hoping I can get a more expert answer here. I'm ordering my first jacket from a local tailor after previous orders from W.W. Chan. Since he's right here for multiple fittings, I'd like to work on perfecting fit and silhouette. I'm trying to decide if I can or should have smaller armholes than on my Chan. When I lift the shoulder of my Chan jacket until the armscye comes in contact with my armpit, I can fit about two and a half fingers (about one and three quarters inches) between the jacket and the top of my shoulder. Is this as high as I want to go, or should I ask for a smaller armhole? Second, because this is an odd jacket, not a suit, and I'd like to be able to wear a light sweater under it, I want a little more room in the upper arm. Is the desire for a roomier upper arm incosistent with raising the armhole?

Not the most experienced but I can pass on my journey after a lot of experimenting in getting a better fit.

It can matter a lot how the shoulders of the suit fit. Rather than disturb the lie of the shoulder by lifting it, simply reach in your jacket with the opposite hand and feel the seam under your armpit. I prefer it pretty snug and what you describe sounds like a lot. Put on an off the rack suit and do the same thing to understand why you want bespoke.

The goal is not the high armpit specifically but freedom of movement for the arm. Lift your arm and see where the jacket lifts first. The drape around the bottom of the armhole in the front and back also impacts freedom of movement. Discuss this with your tailor and experiment until you find what works for you. This will likely take more than one jacket to find your place. Look for comfort and freedom of movement. When you move freely and are comfortable you look better.

This is an interesting question. The cutter should have the correct answers. The fit of the shoulders is basically from mid shoulder to mid shoulder. This leaves the ends of the shoulder to be loose enough for body movement inside. Esxcess above is for looks (fashion). To much excess below (armpit) is slopy craftsmanship. The last point depends on the shirt and/or the sweater to be worn with the coat. For example, if the sweater armhole is deep and the coats is not there will be conflict. So, the coats should be up to the shirt or sweater armpit without conflict. Custom shirts and sweaters would be a big help for a well cut coat.

When people, who know, talk about high armholes this is about the armpit area. Armpit cuts that go down to the waist is no good. So many of the factory garments have the lower part of the armhole so far down it is completely ridiculous.

Greger provided some good insight and advice. On a sleek city suit coat you want the armhole to be as small as possible without becoming uncomfortable; of course, your shirts need to have an equally small armhole, so the sleeves don't bunch up at the armpit with the coat on.
On an odd jacket to be worn over a sweater, however, you need to leave a little more room in the chest, back, waist, sleeve AND at the armpit - unless you plan to wear tight turtleneck sweaters that fit like a glove.

Most sweaters to be worn over a shirt won't be that tight and the coat needs a bit extra room under the arm, too, so the sweater sleeve doesn't bunch up.