The lug width — the distance between the watch lugs where the strap attaches — is the most important measurement to know when choosing a strap. Getting it wrong by 1 mm means a strap that wobbles or won’t attach. The good news: measuring it takes 3 minutes and a ruler in millimetres. Let me explain how to get it right the first time.
What is the lug width of a watch?
The lugs (also called “horns”, or in Italian anse) are the two prongs above and below the watch case. Between them passes the spring bar (the metal spring-loaded pin) that holds the strap. The lug width is the internal distance between the two lugs — measured “inside to inside”, not from the outside of the case.
Standard lug widths are even numbers: 18, 20, 22 mm. Odd numbers (19 and 21) are common on vintage watches or Italian pieces from the 1960s-70s. Below 16 mm you find only women’s watches or small vintage pieces. Above 24 mm: large chronographs or modern sports watches.
What do you measure the lug width with?
Three options in order of precision:
- Digital caliper — the best by far. Accurate to a tenth of a mm. Costs 10-15 € on Amazon. This is what I use in the atelier.
- Millimetre ruler — accurate to half a mm. Works perfectly well. Important: it must have a scale in mm, not only cm.
- Caliper app on smartphone — works but less precise. Only if you have nothing else.
Where are the lugs, and where do you measure?
Turn the watch over: caseback facing up, dial facing the table (with a soft cloth beneath). The lugs are the two “beaks” that protrude above and below: that’s where the spring bar passes. On vintage or square-shaped watches, the lugs may be less obvious — look for where the current strap begins or where the holes for the spring bar are located.
Do you measure inside or outside the lugs?
Position the caliper or ruler between the two lugs, not over the case. The tip of the caliper touches the inner face of the lug (the one facing the centre of the watch). Read the measurement in millimetres.
If you have a ruler, measure by aligning the zero with the inner face of one lug and read where the inner face of the other falls. Keep the ruler straight, parallel to the spring bar.
Can you read the measurement from the existing strap?
If the watch already has a strap, there’s a quick trick. Remove the spring bar and measure the spring bar itself with the caliper — the length of the spring bar corresponds to the lug width. It’s the fastest and most reliable method, because the spring bar is designed exactly for that lug width.
How do you cross-check the measurement for reference?
Search Google for “[watch model] lug width” — example: “Rolex Submariner 116610 lug width”. Most models have a documented lug width. Always verify with at least two sources (specialist forums or watch databases) and make sure the sources cite the exact reference (not only the collection name).
If you’re looking for the lug width for vintage watches or rare references, at Milano Straps we have a database of over 40,000 models with verified lug width.
What mistakes lead to the wrong measurement?
- Measuring the outer case instead of the inside of the lugs — this is the first mistake. The outer case is 2-4 mm wider than the lug width.
- Measuring the strap in width — the strap may be slightly narrower than the lug width (by 0.2-0.5 mm). Use the spring bar as reference.
- Rounding to the cm — the difference between 20 mm and 21 mm is enormous for the fit. Be precise to the mm.
Now that you know your lug width, you can look for compatible straps. If you have an “unusual” lug width (19 mm, 21 mm, 23 mm) many manufacturers don’t produce them: at the Casati Milano atelier we craft bespoke straps for any lug width, including rare vintage references. If you want to verify a watch in person, come to Via XX Settembre 15 with the piece — by appointment only.