Lug Width and Strap Sizing: How to Buy a Strap That Fits

Lug width is the distance between the two lugs, the horns on each side of the case where a strap attaches. It is measured in millimeters and is the number that decides whether a strap will fit. Common sizes are 18, 20 and 22 mm, with 19, 21, 24 and wider sizes appearing on some models.

The easiest way to find it is to read the specifications. Brands usually list the lug width, sometimes called the strap width, in the technical details. If you cannot find it, measure it yourself with calipers or a small ruler across the gap between the lugs, from the inside of one to the inside of the other. Measure at the point where the spring bar sits, which is the narrowest part.

Straps are sold by the width at the lugs, and many taper toward the buckle. A strap listed as 20/18 is 20 mm where it meets the case and 18 mm at the buckle. Tapering looks more refined on smaller wrists, while straight straps look sportier and sturdier.

The strap is held on by spring bars, small spring-loaded rods that sit between the lugs. Many modern straps have quick-release spring bars with a little tab, so you can swap a strap without tools. Standard spring bars need a special tool and a careful hand to avoid scratching the case.

A few tips avoid problems. Buy a strap that matches the lug width exactly, because a smaller one leaves a visible gap and a larger one will not fit. Check the lug-to-lug distance too, since a long, thick strap on a short case can overhang. And if the lugs are drilled or the case has unusual shapes, such as an integrated bracelet, you may need a model-specific strap.