Strap Measurements and Compatibility Checklist: Lug Width Is Not Lug-to-Lug

TrustyTime editorial team · 2026-11-02 · Practical guide

Changing a strap is one of the easiest ways to change how a watch looks and feels. But a strap that’s a millimetre off, too thick or the wrong length can be uncomfortable or insecure. A few measurements taken before you buy will prevent most problems.

Lug width is not lug-to-lug

These two measurements are often confused:

• Lug width is the inside distance between a pair of lugs, where the end of the strap sits. A strap has to match this number.
• Lug-to-lug is the distance from the tip of the top lugs to the tip of the bottom lugs. It describes how long the case sits on your wrist. It doesn’t tell you which strap fits.

How to measure lug width

1. Remove the existing strap, or measure the strap end where it meets the case.
2. Use digital or vernier calipers if you have them. Otherwise, use a ruler with millimetre markings and a magnifier.
3. Measure between the inner faces of the lugs, at the spring bar holes.
4. Repeat on the other pair of lugs. They’re usually the same, but check.

Many watches use even millimetre widths, but odd widths exist. Don’t round a measurement to the nearest common size without checking. A strap that’s too narrow can leave a gap and put stress on the spring bars, and one that’s too wide may not fit at all.

Other compatibility points

• Strap thickness at the end: thick leather or rubber may not fit in the gap between the spring bar and the case. Look at how much clearance the current strap has.
• Spring bars: note whether yours are standard, quick-release or a thicker type. The bar’s diameter must suit both the lug holes and the channel in the strap.
• Curved ends and fitted bracelets: straps or bracelets with shaped ends are made for one case profile. An end that fits one case may leave gaps on another, or not fit at all.
• Taper: many straps narrow from the lug width to a smaller width at the buckle. Check the buckle width if you plan to reuse an existing buckle or clasp.
• Pass-through straps: one-piece straps that run under the case add height and may make a thick watch sit higher.

Strap length

Two-piece straps are usually described by the length of each piece. To estimate what you need, measure your wrist and subtract the watch’s lug-to-lug length. What’s left is roughly what the two strap pieces and the buckle must cover, plus some overlap for the tip. Compare that with the strap’s listed lengths and number of holes. If you’re between sizes, check whether extra holes can be added.

Fitting safely

• Use a proper spring bar tool and work over a soft cloth.
• Cover the lugs with low-tack tape to reduce the risk of scratches.
• After fitting, push and pull gently on each end to confirm both spring bar tips are seated in their holes.
• Check again after a day of wear.

Compatibility checklist

• Lug width, measured in millimetres
• Strap end thickness and the clearance available
• Spring bar type and diameter
• Straight or curved strap end
• Buckle width and taper
• Wrist circumference minus lug-to-lug length
• Whether the material suits your use. Leather and some fabrics don’t cope well with water or sweat.