US Men’s Size M to UK

Almost every men’s clothing size is really a coded way of describing one measurement — the chest circumference — but each region codes it differently, and two different styles of code sit side by side. Casual clothes (T-shirts, sweaters, casual shirts) use letter sizes — XS, S, M, L, XL and up — which are the same letters worldwide but only ever describe a chest range, not an exact number. Tailored clothes (suits, blazers, dress shirts) use numeric sizes: in the US and UK the number is simply the chest measured in inches, so a 40 is a 40-inch chest, while most of continental Europe — Italy, France, Germany, Russia — adds ten, so that same chest is a EU 50. That is the whole trick: EU = US + 10, and US = chest in inches. Because a letter covers a two-inch-or-so band of chest, converting to a letter always snaps to the nearest one, and different brands cut an M or a 40 slightly differently. To use any of it well, measure your chest at its fullest point with the tape level and snug, then read across: a 96–cm (38–inch) chest is an M, a US 38 and a EU 48; a 107–cm (42–inch) chest is an L, a US 42 and a EU 52. Treat the letters as approximate, check the brand’s own chart when you can, and size up if you are between sizes or prefer a relaxed fit.