Lug-to-Lug Explained: Understanding the Most Important Watch Sizing

Many factors go into the purchase of a new watch —  from pricing to colorway to the choice of movement and materials — but perhaps none are more make-or-break for most consumers than sizing. Watches, of course, being three-dimensional objects, there are multiple areas of measurement to consider, though most watch brands tend to narrow it down to the two most basic: the diameter (or in the case of non-round watches, the dimensions) of the main case and the case’s overall thickness, i.e. how high it will rise on the wrist. However, neither of these accounts fully for how large or small the watch will wear on the wrist. For that, you will need the lug-to-lug measurement, sometimes referred to more simply as the “length,” with the diameter deemed in shorthand as the “width.”

The lugs, sometimes called “horns,” are the protruding parts of the case that connect it to the bracelet or strap. The distance from the tip of the top lugs to the tip of the bottom lugs is perhaps the most important factor that affects not only how large the watch “wears” on the wrist but also how comfortable it is. (This measurement should not be confused with another occasionally listed stat, the “lug width.” The latter, which is perhaps most useful for those looking to swap out other straps or bracelets on their watch, refers to the distance between the lugs on each side of the case, i.e., the span in which the strap or bracelet fits inside them. If a watch has a lug width of 20mm, for example, any replacement strap would have to be 20mm wide, not wider or thinner.)

So, we have a diameter measurement and a lug-to-lug measurement: which is more accurate? In actuality, they sort of work together. Most “round” watch cases aren’t actually round but consist of a round bezel and a round caseback mounted on a curvilinear middle piece that extends outward via the lugs to fasten to the bracelet or strap. 

When the lug-to-lug measurement is close to the case diameter, the watch tends to “wear” smaller, i.e. the Seiko “Turtle” dive watch, whose case diameter is a rather hefty 45mm but whose lugs are very short and tight to the case, 47.7mm from lug to lug. By contrast, the Hamilton Khaki Field Mechanical case is only 38mm in diameter but its lugs widen out to 47mm, making it appear somewhat larger. 

Lug to lug measurement is particularly important on watches that are not round, like the Cartier Tank and Jaeger-LeCoultre Reverso (above). The latter watch’s 27.4mm width makes it sound deceptively dainty, but its lug-to-lug span of 45.2mm gives you a better idea of how much presence it will actually have on the wrist.

By way of oversimplification, a watch’s lug width is likely to be the largest number among its stats, and thus the truest indicator of exactly how much wrist real estate it’s going to occupy once it’s worn.If it’s not available among the given stats of a watch you’re considering buying (or selling), you can always make the calculation yourself, using calipers or even a simple ruler with millimeters. Simply place the watch on a flat surface, preferably removed from the strap or bracelet, and measure from the tip of the top lug to the tip of the bottom one. Of course, you also can’t go wrong with just trying on the watch and seeing how it looks and feels on the wrist: personal taste, regardless of minuscule measurements, is always the final arbiter, after all.