Every strap has two widths. The first, the lug width, is where the strap meets the watch case, and it is covered in how to measure lug width. The second is at the other end, where the strap passes through the buckle or folds into a deployant clasp. That is the buckle width, and it matters as soon as you want to keep a buckle or clasp you already own.
This guide explains what buckle width is, how to measure it, and how it changes depending on whether you wear a pin buckle, a deployant or a butterfly clasp.
Buckle width and lug width are not the same
Many straps are wider at the case than at the buckle. The strap narrows gradually along its length, which is called the taper. How much it tapers is your choice: a strap with a 20 mm lug width can narrow to 18 or 16 mm at the buckle, or stay at 20 mm all the way with no taper at all. A stronger taper looks finer and more classic; a straight strap looks sportier and more modern. The watch strap sizing guide shows how the measurements relate.
What matters for fit is simple: the buckle end of the strap must match the inside width of your buckle or clasp. Too narrow, and the strap slides from side to side in the buckle. Too wide, and it will not pass through at all, or it creases at the edges.
How to measure buckle width
On a pin buckle
- Look at the buckle from the side where the strap enters it.
- Measure the inside distance between the two sides of the buckle frame, in millimetres. This is the width of strap the buckle is made for.
- Many buckles also have the width stamped on the inside of the frame.
On a strap you already own
If you have a strap that fits your buckle well, measure across the strap at the very end that goes into the buckle. That figure is the buckle width you need.
On a deployant or folding clasp
Measure the inside width of the slot or bar where the strap is attached to the clasp. For a deployant that replaces the pin buckle, this works in the same way as a buckle. For a butterfly clasp, which opens on both sides in the middle of the strap, see the section below.
As with lug width, do not round a measurement that falls between two sizes. Measure again with a calliper, or send me the reference of your buckle or watch.
Pin buckle, deployant or butterfly clasp
The type of closure changes how the strap end is built, not just how wide it is.
- Pin buckle. The classic closure. The strap has a row of holes on the long side and a loop for the end. Buckle width is the key measurement. For the Cartier Tank, the configurator offers buckle widths of 12, 14, 16 and 18 mm, and you can order the strap with a steel pin buckle in a silver or gold finish, or without a buckle if you are keeping your own.
- Deployant clasp. A folding clasp that replaces the buckle. The strap is shaped to sit in the clasp, and the length is set so that the clasp sits under the wrist. When you choose a strap "for deployment buckle", the end is made for that type of clasp.
- Butterfly clasp. A clasp in the centre of the strap that opens on both sides. The strap is made in two equal halves without holes, as on the Cartier Santos 100. The Cartier Santos 100 strap guide explains this construction in detail.
For the current Cartier Santos, the configurator asks whether the strap is for a deployment buckle or a butterfly buckle, because the strap is built differently for each. For the Santos-Dumont, you choose the buckle width (14, 16 or 18 mm) and whether the strap is for a deployment buckle or a standard buckle.
Keeping your original buckle or clasp
Many people want to keep the buckle or clasp that came with their watch, and it is usually the right choice: it matches the case, and it carries the maker's name. To do that, the strap has to be made for its exact width and type. In the configurator, choose the buckle width that matches your buckle, and the closure type you use.
Straps made for a deployant or butterfly clasp are supplied without the clasp: you keep and reuse your own. Where the configurator offers a pin buckle, as on the Tank, the buckle you choose is sent with the strap. If your watch came without a clasp, or you want a different one, please write to me before ordering.
Quick reference
| Question | Answer |
|---|---|
| What is buckle width? | The width of the strap where it meets the buckle or clasp, in millimetres. |
| Is it the same as lug width? | Not necessarily. It can be narrower (a tapered strap) or the same (a straight strap). The choice is yours. |
| How do I measure it? | Inside width of the buckle frame, or across the end of a strap that fits your buckle. |
| What about a butterfly clasp? | The strap is made in two equal halves without holes, for that clasp. |
| Can I keep my original buckle? | Yes. Choose its width and type in the configurator. |
