What is lug width?

The gap between the two lugs that hold the strap, in millimetres. A new strap must match it exactly: 20 mm lugs take a 20 mm strap.

Measure it in 30 seconds

1. Take the strap off, or look at the back of it: many straps print their width.
2. Measure the inside gap between the lugs with a caliper or a millimetre ruler.
3. Round to the nearest whole millimetre. Most watches use 18, 20 or 22 mm.

Strap, quick release or system?

Most watches use spring bars, so any strap of the right width fits. Many smartwatches use their own band system instead, such as Apple Watch bands or Garmin QuickFit.