Your dress shirts really shouldn't come in standard sizes like small, medium or large. But when your shirt tag looks like a lottery ticket—15 , 32/33—it can be a bit confusing. This isn't the time to guesstimate. The numbers are precise measurements, so make sure you're sized up correctly. Below, how to ensure a perfect fit.
While you can simply measure the circumference of your neck, a safer bet would be to take a shirt that fits you well and record the length from the collar button around to the tip of the buttonhole.
Bend your arm into a 90-degree angle. Start measuring from the middle of your back (just below your neck), across your shoulder and down over your elbow to your wrist.
Some shirts, especially American ones with "athletic" or slimmer cuts, will list a waist size as well.
