How to Measure Watch Lug Width for Strap Replacement
By James Alderton . 6 min read . Updated June 2026
The single most common mistake when buying a watch strap is ordering the wrong width. A strap that is 1mm too wide will not thread through the lug gap; one that is too narrow will have visible lateral play and look sloppy. Measuring correctly takes less than two minutes with the right tool. This guide explains how to do it, what to do with tapered or curved lugs, and lists common widths for popular watches so you can shop with confidence. Once you have the measurement, finding the right Hemsut Classic Nylon NATO Strap , Barton Quick-Release Genuine Leather Strap , or Barton Milanese Loop Watch Bracelet is straightforward.
The short answer
Use digital calipers or a millimeter ruler held flat across the inside faces of the lug tips. Most watches measure 18mm, 19mm, 20mm, or 22mm. Common reference widths: Rolex Submariner 20mm, Omega Seamaster 300M 20mm, Seiko SKX 22mm, Seiko 5 Sports 22mm, Tudor Black Bay 22mm, Orient Mako 22mm, Casio MDV-106 18mm.
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What is lug width and why does it matter?
The lugs are the protruding arms on either side of the watch case where the strap attaches. Lug width is the internal measurement of the gap between the two lug tips at the point where the spring bar seats. This is where the strap must fit.
A strap must match the lug width exactly. Even 0.5mm too wide and the strap end will not seat flush with the lug face. Even 1mm too narrow and the strap will have lateral play that allows the watch to slide on the wrist, which looks wrong and can cause the case to contact the bracelet end link repeatedly.
How to measure with calipers
Digital calipers are the most accurate method. The Esslinger Watchmaker Starter Tool Kit includes a basic pair along with the other tools you need for strap work. Open the caliper jaws and place the inner measurement tips between the inner faces of the lugs at the spring bar axis. Close gently until both tips contact the lug faces without applying pressure that would push the lugs apart. Read the measurement.
If you do not own calipers, a metal millimeter ruler held flat and viewed straight down from above works for most measurements. Look at the inner lug tips from directly above and read the gap between them.
Esslinger Watchmaker Starter Tool Kit
A beginner kit from Esslinger that bundles a spring bar tool, adjustable case back opener wrench, 5x loupe, case cushion, and watchmaker screwdrivers in a compact roll pouch. A genuine starter toolkit for DIY watch maintenance.
Common lug widths by watch reference
Knowing the reference widths for popular watches means you can shop for straps confidently without measuring each time. Rolex Submariner and GMT-Master II: 20mm. Omega Seamaster 300M (current generation): 20mm. Seiko SKX007 and SKX009: 22mm. Seiko 5 Sports SRPD series: 22mm. Tudor Black Bay 58: 20mm. Tudor Black Bay 41: 22mm. Orient Mako II: 22mm. Casio MDV-106 Diver: 18mm. IWC Pilot Mark XX: 20mm. Longines HydroConquest: 21mm (less common, verify before ordering).
These measurements are for reference only. Always measure your specific watch if you have any uncertainty, particularly for older references that may have been revised across production runs.
Tapered and curved lug cases
Some watch cases have lugs that curve downward toward the wrist. A strap with curved ends seats more cleanly against these cases than a straight-end strap. The ZULUDIVER FKM Rubber Dive Strap is an example of a dive strap made with curved ends for popular sport watch case profiles.
Tapered lugs, where the lug gap is wider at the case than at the spring bar axis, are less common but exist on some vintage designs. Measure at the spring bar axis (where the spring bar seats), not at the outermost tip of the lug.
ZULUDIVER FKM Rubber Dive Strap
A fluoroelastomer rubber strap made for dive watches, with a curved end profile for popular sport watch lug shapes, a signed stainless tang buckle, and a ventilated design for underwater comfort.
Featured in this guide
Bergeon 6767-F Spring Bar Tool
The Swiss-made professional spring bar tool used by watchmakers and serious collectors. A forked stainless tip with a replaceable plastic grip handle. The benchmark tool for strap changes on fine watches.
Esslinger Watchmaker Starter Tool Kit
A beginner kit from Esslinger that bundles a spring bar tool, adjustable case back opener wrench, 5x loupe, case cushion, and watchmaker screwdrivers in a compact roll pouch. A genuine starter toolkit for DIY watch maintenance.
Hemsut Classic Nylon NATO Strap
A straightforward woven-nylon NATO from Hemsut with stainless steel hardware and a double-pass keeper. Clean execution at a budget price, available in 18mm, 20mm, and 22mm.
Barton Quick-Release Genuine Leather Strap
A tool-free quick-release leather strap from Barton with a push-button spring bar mechanism. Genuine leather upper, smooth lining, and stainless steel buckle. The practical choice for owners who swap straps often.
ZULUDIVER FKM Rubber Dive Strap
A fluoroelastomer rubber strap made for dive watches, with a curved end profile for popular sport watch lug shapes, a signed stainless tang buckle, and a ventilated design for underwater comfort.
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