How to measure your watch's lug width
Lug width is the inside distance between the lugs of your watch case, where the spring bar holds the strap. It is the width of the strap at the watch, the one measurement you need before you order, and the strap has to match it to the millimeter.
Three ways to find your lug width
From the most reliable to the least:
1. Look it up for your exact model
The maker's specifications list it as lug width, strap width or bracelet width. Search for your watch's reference number, found on the caseback or in the papers, together with "lug width". Go by the exact reference: the same model can change its lug width from one generation to the next.
2. Read it off your current strap
Many straps carry their size on the underside, near the lug end: a single number such as 20, or two numbers such as 20/16. The first number is the lug width. Trust it only if the strap fits well, since a replacement strap may be the wrong size.
3. Measure between the lugs
Take the strap off and measure the inside distance between two lugs, where the spring bar sits. A caliper is the most accurate tool; a ruler with millimeter marks works if you hold it flat against the case.
Lug widths are almost always whole millimeters, so a reading of 19.7 means 20 mm. Measure the other end of the case too: the two are almost always the same, and the second reading confirms the first.
Common lug widths
Most watches take 18 to 22 mm, and odd sizes such as 19 and 21 mm are common. Half the case diameter is a rough guess at best: only the number you look up or measure is reliable.
| Lug width | Typical watches |
|---|---|
| 16 mm and less | Women's and small watches, often 12 to 16 mm, and many vintage pieces |
| 18 mm | Dress watches and smaller cases, often 34 to 38 mm across |
| 19 mm | Many dress and vintage watches; easy to mistake for 18 or 20 mm |
| 20 mm | The most common size, on many watches from 38 to 42 mm |
| 21 mm | Some modern sports and dress watches |
| 22 mm | Larger sports, dive and field watches, often 42 mm and up |
| 24 mm and more | Big pilot's and dive watches |
Taper: the width at the buckle
Most straps narrow towards the buckle. Shops write the two widths together: 20/16 means 20 mm at the lugs and 16 mm at the buckle. The first number has to match your lug width. The second is a matter of style, since a stronger taper looks more elegant and a straight strap sportier, and it has to match your buckle if you keep the one you have.
Spring bars
Straps attach to the lugs with spring bars, small spring-loaded pins held in holes on the inside of the lugs. They come in lug widths too, so use the ones that come with your new strap or check that yours match. Quick-release spring bars have a small lever and need no tool.
Lug width is not lug to lug
Lug to lug is the length of the watch, from the tips of the top lugs to the tips of the bottom lugs. It tells you how large a watch wears on your wrist, not which strap fits it.
Watches without regular lugs
Watches with an integrated bracelet, where the bracelet flows straight out of the case, and many smartwatches take straps made for that model only. A regular strap does not fit them.
Found your lug width?
Open the try-on, pick your width under Lug width and see which straps suit your watch.
Lug width questions
Can I wear a strap that is 1 mm narrower or wider?
One that is 1 mm narrower goes on, but it leaves a gap at the lugs and slides along the spring bar. One that is 1 mm wider only goes in if it is soft, such as a NATO or a supple leather strap, and it bunches at the lugs; rubber and stiff leather do not fit. Choose the width that matches.
What does 20/16 mean on a strap?
The first number is the width at the lugs, the second the width at the buckle. 20/16 is a strap for a 20 mm lug width that tapers to 16 mm at the buckle.
Is lug width the same as case size?
No. Case size is the diameter of the case; lug width is the gap between the lugs. Two watches of the same case size can take different straps, so look it up or measure it for your model.
Does the try-on measure my lug width?
No. It shows how a strap looks on your watch. Once you know your lug width, the Lug width filter in the try-on shows only the straps made in your size.