What is lug width on a watch?
The distance between the two lugs of the case, where the strap goes in, measured in whole millimetres. It is set by the watch, not by the strap, and it is the one number a strap has to match before anything else about it matters.
the range of lug widths measured across 41,485 watches. 20 mm is the most common, on 36.4%. Measured 2026-10-24.
Where the number is on the watch
The lugs are the four horns that extend from the case to hold the strap. Between each pair runs a spring bar, and the strap end slides over it. Lug width is the inside gap between those two lugs: the only width a strap can have at that point. A 20 mm strap on 20 mm lugs fills the gap exactly; 19 mm leaves it loose and rattling, 21 mm does not go in.
Three measurements that are not the lug width
- Not the case diameter. A 40 mm case does not take a 40 mm strap, and there is no fixed ratio. At 42 mm, the most common case size, references take 20 different lug widths. Why the rule of thumb breaks.
- Not the overall length of the case, tip to tip. Collectors call that lug-to-lug: the distance from the top end of the case to the bottom end, usually 46 to 48 mm on a 40 mm case. It tells you whether the watch sits well on your wrist, not which strap fits. The two are often searched together and are not the same number.
- Not the strap width at the buckle. Most straps taper: 20 mm at the lugs, 16 or 18 at the buckle. The second number is a design choice. The first is the watch’s.
Why it is the number that decides
Everything else about a strap is a preference: leather, colour, stitching, length. Lug width is a constraint. Get it wrong by one millimetre and the strap either will not fit or will not stay. That is why every reference in the database carries it, and why it is the first thing to check before looking at a single strap.
The measured sizes, from smallest to largest
Across 41,485 measured watches, lug widths run from 12 to 26 mm. 20 mm covers 36.4%; the next two sizes, 22 and 18 mm, cover 16.8% and 9.6%. Odd numbers are real: 18.2% of watches take 19, 21, 23, 17 or 15 mm. And 2,640 watches, 5.7%, have no lug width at all, because the bracelet is built into the case.
- 20 mm36.4% of watches
- 22 mm16.8% of watches
- 18 mm9.6% of watches
- 16 mm7.3% of watches
How to find the lug width of your watch
- Look it up. The measurement has been taken for 41,485 references. Search yours and the number is on its page.
- Measure it. If the watch is not in the database, or you want to check: take the strap off, put a caliper inside the gap, read whole millimetres. The three steps and the two mistakes.
Check your own reference
Family averages are the reason people order the wrong size. Your reference has its own measured number, and it is in the database.
Search your referenceOther questions
- What size watch strap do I need?Width comes from the watch, length from your wrist. Every lug width in one chart, with the brands that use it.12–26 mm
- Does lug width change within the same watch family?70.3% of watch families use more than one lug width. Knowing the family is not enough.70.3%
- What is the most common lug width on watches?20 mm, on 36.4% of measured watches. What the rest of the distribution looks like.20 mm
- Can a watch have an odd lug width like 21 mm?One watch in six takes an odd size. 21 mm is not a rounding error.18.2%