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Ringmesser öffnenWatch strap size · No sign-up
A 20 mm strap will not fit an 18 mm watch.
Lug width is the one measurement here with no tolerance — it either fits or it doesn't. Measure the gap between your lugs on a calibrated screen and buy the exact size.
Step 1. Calibrate the screen — or reuse the scale from the ring sizer.
Using your saved calibration.
Screen scale: — CSS pixels per mm
Step 2. Hold the watch against the screen, strap removed, and widen the gap until the markers sit against the inside of each lug.
Measured: —
Don't have the watch to hand?
Strap width to buy
—
Step 3 (optional). Strap length is a separate number from lug width, and has real tolerance.
Two numbers, often confused
Lug width
The gap between the lugs, where the strap attaches. Always an even number of millimetres. Must match exactly — there is no close enough.
Strap length
How far it goes round your wrist. Sold as short, regular or long, and unlike width there's genuine room for error, because the buckle holes give you a range.
A third number — case diameter — is neither of these, and mistaking it for lug width is the most common way a strap arrives unusable. A 40 mm watch is 40 mm across the face; its lug gap is usually 20 mm.
How to measure it
- 01
Take the old strap off
The lug width is the gap between the lugs — the two horns the strap sits between — and you cannot measure it accurately with a strap in the way. Most spring bars release with a small tool, or a fingernail on a quick-release strap.
- 02
Hold the case against the screen
Calibrate the screen first, then widen the two markers until they sit against the inside face of each lug. Look straight down at the screen rather than at an angle — viewing angle is the biggest source of error at this scale.
- 03
Buy the exact width
Straps are made in even millimetres, so the tool snaps your measurement to the nearest real size. If your reading is more than about 0.8 mm from any manufactured width, something is wrong with the calibration or the alignment — it isn't a 19.4 mm strap, because those aren't made.
Case diameter to lug width
A fallback for when the watch isn't to hand. This is a convention rather than a standard — makers vary, and dress watches run narrower than divers at the same diameter — so measure the gap directly whenever you can.
| Case diameter | Usual lug width |
|---|---|
| 26–32 mm | 12 or 14 or 16 mm |
| 33–36 mm | 16 or 18 mm |
| 37–39 mm | 18 or 20 mm |
| 40–42 mm | 20 or 22 mm |
| 43–46 mm | 22 or 24 mm |
| 47–55 mm | 24 or 26 mm |
Strap lengths
Quoted as two figures — the long and short halves either side of the case.
Sometimes sold as XS or 'ladies'. Also the right choice for a large case on a small wrist, where a regular strap leaves too much tail.
The default, and what a strap is unless the listing says otherwise.
Sometimes sold as XL. Worth choosing if a regular strap leaves you on the last hole.