Here's a sharp suit from Brioni.

Measured flat:
Armpit to armpit 22.5"
Narrowest below armpits 21"

Important. Because this jacket has no size tag, the above size can only be considered my estimation. I strongly recommend measuring a similar jacket that fits you well and comparing your measurements to those above.

Customer satisfaction is always guaranteed. International Buyers – Please Note: Import duties, taxes, and charges are not included in the item price or shipping cost. These charges are the buyer's responsibility. Please check with your country's customs office to determine what these additional costs will be prior to bidding or buying. Customs fees are normally charged by the shipping company or collected when you pick the item up. These fees are not additional shipping charges. We won't under-value merchandise or mark the item as a gift on customs forms. Doing that is against U.S. and international laws.