If you've ever bought two shirts in the same size from two different brands and had one choke you and the other gape, the problem usually isn't the shirt — it's how the size was measured in the first place. A collar size is one number, in centimetres or inches, and it only means something if it was taken correctly.
What you'll need
- A soft, flexible tape measure (a fabric one, not a metal one)
- A shirt with a collar you already own and like the fit of, for comparison
- A mirror, or a second pair of hands
The three-minute method
Stand naturally, don't tuck your chin, and wrap the tape around the base of your neck — roughly where a buttoned collar would sit, just above the collarbone. Keep the tape snug but not tight enough to leave a mark. Note the number, then add 1.5 centimetres (about half an inch) for breathing and swallowing room. That's your collar size.
The 1.5 cm allowance matters more than people expect. Measure your neck exactly and buy to that number, and a shirt that felt fine in the fitting room will feel tight by lunch, once you've eaten and the fabric has settled. A little room at the collar is not a loose fit — it's a collar that still closes comfortably eight hours into the day.
Cross-check with a shirt you trust
Lay a shirt you already wear comfortably flat on a table, button the collar, and measure from the centre of the button to the centre of the buttonhole. That distance should be close to the number you just took from your neck. If it's noticeably different, your neck has likely changed size since you bought that shirt — which happens more often than people think, especially after a change in training, diet, or simply age.
If you're between two sizes
Go up, not down. A collar that's a touch generous can be tightened with a slightly firmer stand or worn open at the top button; a collar that's too small will cut, no matter how well the rest of the shirt fits. If you're consistently between sizes, or your neck is a noticeably different width at the front than the back, a made-to-measure collar — cut to your exact shape rather than a standard curve — will solve more than another size chart ever will.
A collar size is only as good as the moment it was measured in. Measure at the end of a normal day, not first thing in the morning.
Once you have a number you trust, write it down somewhere you'll actually find it again. It's the single most useful piece of information you can hand a shirtmaker, and it doesn't change often — you'll likely use the same measurement for years.
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