Getting the size right the first time

The fastest way to order the right size is to stop reading size charts and go measure a shirt you already like.

Three numbers

Lay the shirt flat and buttoned on a table. Measure the chest from armpit seam to armpit seam, then double it. Measure the shoulder across the back, seam to seam. Measure the sleeve from the shoulder seam to the end of the cuff. Those three numbers describe how a shirt fits you better than your chest circumference ever will, because they describe a garment you have already worn and approved.

Where stretch changes the maths

A woven cotton shirt has to be cut with ease built in, usually 15 to 20 cm more than your chest, or you cannot raise your arms. A fabric with elastane in it borrows that room from the stretch instead of from the cut. The same measured chest then reads slimmer on the body and still moves. Between two sizes and you want it close, take the smaller one. Want it to sit away from the body, take the larger one and accept that the shoulder will drop a little.

The shoulder is the one you cannot fix

A tailor can take in a body, shorten a sleeve, move a button. Moving a shoulder seam means rebuilding the entire top of the shirt and costs more than the shirt. So when two sizes both look plausible, choose on the shoulder. The seam should land where your arm starts to curve down, not on top of the deltoid and not hanging past it.

Sleeve length

Arms down, the cuff ends at the wrist bone. Arms forward, it should not retreat past it. If you wear a watch, add half a centimetre. Most men order sleeves too long, because that is how shirts have always arrived.