Watch strap width is normally the clear distance between the case lugs at the strap attachment, measured in millimeters. Measure that opening on your exact watch before ordering a replacement. Then check the strap's buckle-end width, length and attachment hardware. A nominal width alone cannot guarantee compatibility with a curved, integrated or proprietary case. If the attachment is unclear, ask the maker or an authorised service centre rather than forcing a strap into place.
Where exactly do I measure watch strap width?
Look at the two lugs that hold the strap at the top or bottom of the case. Measure the clear inside distance between their inner faces where the strap meets the case. A small caliper gives a cleaner reading than a flexible tape. If a ruler is all you have, hold it flat and read the opening in millimeters without including the metal lugs. Measure both ends if the case looks asymmetric.
Longines' official strap guide identifies this between-lug distance as the strap size and gives 18, 20 and 22 mm as common examples. Those are examples, not a recommendation for your watch. A 20 mm strap should not be assumed to fit a 19 mm opening just because leather can compress, and a loose narrow strap can leave the spring bar unsupported.
If the original strap is still attached, check its printed width or purchase documentation, but verify the case measurement. A previous owner may have installed a nonoriginal strap. Photograph the attachment before removal so you can compare shape and hardware later. Note whether the strap fills a shaped recess, curves around the case or uses a visible standard spring bar.
Is lug width the same as buckle width?
No. Many straps taper from a wider case end to a narrower buckle end. A strap sold as 20/18 mm is typically 20 mm at the lugs and 18 mm at the buckle, though naming varies by maker. If you plan to reuse a clasp or buckle, measure its internal opening separately and confirm the strap's taper and thickness. A correct lug fit can still fail at the clasp.
Also separate width from length. The two strap halves must reach around your wrist with the buckle positioned comfortably and enough adjustment holes left for normal changes in fit. Product listings may specify short, regular and long lengths or list each half in millimeters. Compare those measurements with a strap that already fits you. A wide strap in the wrong length will not become wearable through a different spring bar.
Thickness affects attachment too. A bulky padded leather strap may be nominally the correct width but rub the case or prevent the spring bar from seating. Check clearance behind the lugs and the case shape. A quick-release lever can need extra room. If the watch has a low opening or an integrated profile, request a model-specific recommendation rather than ordering by width alone.
How do I know whether the attachment is standard?
A conventional lug often has two holes and a removable spring bar spanning them. But some watches use screws, captive bars, proprietary quick-release fittings or shaped end pieces. An integrated bracelet may appear to flow directly into the case. Even where the visible opening has a measurable width, a flat generic strap may leave a gap, interfere with the case or lack a secure mounting point.
Inspect the watch's manual or official replacement-strap listing for the exact model. Look for a stated lug width, compatible spring-bar diameter and attachment type. If you cannot find those details, ask support to confirm them. Do not assume a spring-bar tool should be used simply because a strap seems removable. A screw or decorative cap can be damaged by prying.
The VERTU Grand Watch collection covers different variants, and the brand knowledge base reviewed here does not give one universal lug width or promise a standard strap mount. For a Grand Watch, identify the exact edition and ask VERTU which replacement straps and hardware it supports. A number measured across the case is useful to support, but it is not full compatibility evidence.
Can I measure while the strap is still attached?
Often, yes, if the inner lug edges are visible. Use a caliper carefully without scratching the finish. If the strap fills the opening, measure its case-end width and cross-check against the official specification. Avoid squeezing a soft strap so hard that you under-read it. For a curved end or integrated shape, the strap's outer width may not equal the usable inner attachment dimension.
If removal is necessary, protect the case on a soft cloth and follow the watch maker's procedure. Longines advises careful spring-bar release and a light tug after installation to confirm both ends are seated; its guide also notes that metal bracelets can require extra tools. A Seiko manual for an easy-fitting spring bar likewise instructs owners to pull the installed strap to test it. Both are model-specific examples. If the tool slips or the bar will not compress, stop and use a professional.
Keep the original spring bars and end pieces. They may be specific to the case, and a replacement strap may arrive without suitable hardware. If the old bar is bent, corroded or loose, ask for the correct new part rather than reusing it blindly. A secure strap attachment matters more than a perfect colour match.
What should I check on a replacement listing?
Confirm lug-end width, buckle-end width, overall strap length, thickness at the lugs, attachment style, included hardware and stated compatible models. Look for a clear photograph of the case end. If the listing says “fits most watches,” compare its dimensions and end shape with your own watch; that phrase is not a guarantee. Check the seller's return terms before removing protective packaging or altering a strap.
Material choice affects comfort and care. Leather, rubber and textile differ in flexibility, moisture tolerance and the way they sit under a cuff. Our leather-strap guide discusses material and length, while the watch-weight guide covers daylong fit. Choose material after compatibility is established, not before.
For a watch with sensors, confirm that a new strap keeps the case in its intended position without overtightening. A decorative strap that slides may compromise comfort and recording. Test the new assembly over a soft surface, then wear it indoors before taking the watch on a long day. Check both spring-bar ends, buckle and strap stitching again after the first use.
When should I ask a professional?
Use a qualified retailer or authorised service if the lugs are hidden, the case has a proprietary mount, the finish is delicate, a spring bar is damaged or the attachment will not seat positively. Bring the exact watch and proposed strap. Ask them to verify width, hardware and security in front of you. A simple fitting service is preferable to dropping a valuable watch because a near-fit strap slipped free.
The right width is the one measured at the case attachment, but the right replacement also matches shape, hardware and wrist length. Write down all four before buying. This small preparation saves a return, a scratched lug and an insecure fit.
Frequently asked questions
Is a 20 mm strap suitable for a 19 mm lug gap?
Do not assume so. Follow the maker's stated width and attachment specification; forcing or compressing a strap can impair fit.
Can I reuse my watch's buckle?
Only if the new strap's buckle-end width, thickness and attachment match the original clasp or buckle.
Do all Grand Watch models use the same strap width?
The reviewed knowledge base does not establish one shared width. Confirm your exact VERTU edition and approved strap system.
