Lug width explained, with a strap size table

What lug width means

The lugs are the four horns that stick out from the top and bottom of the case. A spring bar runs between each pair of lugs and holds the strap or bracelet. Lug width is the gap between the inner faces of the lugs, measured in millimeters. A strap's width at the end that meets the case must match it.

Lug width is a different number from lug to lug, which is the overall length of the watch from tip to tip and decides how it fits your wrist. Read lug to lug explained for that one. Lug width affects which straps fit and how the watch looks: a wide strap makes a case look bolder, and a narrow strap makes it look dressier.

How to measure lug width

1. 1

   Look up the maker's spec first. Seiko, Orient, Tissot, Hamilton and Mido list lug width or band width in their specs, and many listings repeat it.

2. 2

   If you cannot find it, remove the strap or leave it on and measure the inside gap between the lugs with digital calipers. Calipers give the cleanest reading.

3. 3

   With a ruler, measure the gap at the lug tips with the watch face down on a table. Read to the nearest millimeter.

4. 4

   Round carefully. Most watches use even sizes (18, 20, 22 mm), but 19 and 21 mm are common on dress and Swiss watches. If you read about 20.5 mm, measure again rather than guess.

Note.Measure the gap between the lugs, not the strap you already have. An aftermarket strap fitted by a previous owner may be the wrong width.

Lug width for popular automatic watches

These figures come from the makers' published specs or product listings. Check your exact reference before you buy, because the same family can change lug width between case sizes.

See our Orient picks with full sizes →

Hamilton Khaki Field and Tissot PRX: special cases

Hamilton lists lug width per reference on its own site, and it differs between the Khaki Field Mechanical, the Khaki Field Automatic and the Murph, and between 38, 40 and 42 mm cases. Because the family spans so many sizes, look up the exact reference number printed on the caseback or in the listing rather than relying on a single figure for the line. Our Hamilton Khaki guide lists each model's size so you can match it.

The Tissot PRX has an integrated bracelet: the first link flows straight out of the case with no visible lugs or open spring bar gap. Standard straps do not fit. Tissot sells PRX straps with a matching end piece, and some third-party makers sell PRX-specific straps. When a PRX listing gives a band width figure, treat it as the bracelet's own measurement, not a lug width you can shop by. Learn more in Tissot PRX sizes.

What happens if the strap width is wrong

• Strap 1 mm too narrow: it fits but leaves a visible gap at each side and can shift on the spring bar. Many people accept this on a 21 mm watch with a 20 mm strap, but it looks less tidy.
• Strap 1 mm too wide: you can sometimes squeeze leather in, but it bunches, wears at the edges and can scratch the lugs. Do not force rubber or metal end links.
• Tapered straps: a strap can be 20 mm at the lugs and 16 mm at the buckle. Only the lug end has to match.
• Curved end links: bracelets and some rubber straps are shaped for one specific case and will not fit another watch even at the same width.

Choosing a strap by watch type

Dive watches with 20 or 22 mm lugs suit rubber, silicone and nylon straps that can get wet. See the dive watch straps guide for materials. Field watches look right on canvas, nylon pass-through or leather. Dress watches usually pair with thin leather straps in 18 to 20 mm. Quick-release spring bars, which have a small lever on the bar, make swapping straps easy without a tool.

If you are still choosing the watch itself, a wider lug width gives more strap choice, since 20 and 22 mm are the most common aftermarket sizes. Browse field watches or dive watches under $500 with that in mind.

Frequently asked questions

What is the Seiko 5 lug width? The SKX-style Seiko 5 Sports models such as the SRPD series use 22 mm. Smaller or newer 5 Sports cases can differ, so check the reference you own.

Is lug width the same as band width? Usually yes. Many listings call the strap width at the case band width. On integrated-bracelet watches like the Tissot PRX the band width figure does not describe a standard strap fit.

Can I put a 20 mm strap on a 22 mm watch? It will attach, but it leaves a 1 mm gap on each side and looks undersized. It is better to buy the matching width.

Do I need a tool to change straps? A spring bar tool is cheap and makes it easy. Straps with quick-release bars can be changed with a fingernail.