Open the configurator for any strap and you will find sizes written as two numbers: 110/70, 115/75, 120/80. They look like a code, but they are simply two lengths in millimetres. Once you know what each number measures, choosing becomes much easier.
Two numbers, two pieces of leather
A watch strap is made of two separate pieces.
- The first number is the long side. This is the piece with the holes and the pointed tip. It attaches at the bottom of the case, at 6 o'clock.
- The second number is the short side. This is the piece that carries the buckle. It attaches at the top of the case, at 12 o'clock.
So a 115/75 strap has a long side of 115 mm and a short side of 75 mm. Each is measured from the end that meets the watch case; the buckle itself is not included.
The watch is not part of the measurement. The case sits between the two pieces, so the same strap wears longer on a large watch than on a small one.
The standard sizes
For watches with ordinary lugs and a pin buckle, these are the sizes in the configurator:
| Size | Long side | Short side |
|---|---|---|
| XS | 100 mm | 60 mm |
| S | 110 mm | 70 mm |
| M | 115 mm | 75 mm |
| L | 120 mm | 80 mm |
| XL | 125 mm | 85 mm |
| XXL | 130 mm | 90 mm |
Notice that the two numbers move together. Each step adds length to both sides, which keeps the buckle centred under the wrist as the strap gets longer.
When both numbers are the same: 115/115, 120/120, 125/125
A size with two equal numbers is a different kind of strap. It is made for a butterfly clasp, a folding clasp that sits in the middle of the strap and opens on both sides. Because the clasp is in the centre, both pieces of leather are the same length, and there is no row of buckle holes.
The Cartier Santos 100 is the clearest example: its straps come in 115/115, 120/120 and 125/125 mm. The Santos 100 strap guide explains that construction.
Do not choose an equal-sided size for a pin buckle, or a long/short size for a butterfly clasp. They are not interchangeable.
Sizes by watch
Not every watch is offered in every size, because the right lengths depend on the case and the clasp. These are the sizes for the models I make straps for most often:
| Watch | Sizes offered |
|---|---|
| Cartier Santos (QuickSwitch) | 115/75, 120/80 (the Cartier standard), 125/85; 120/120 for a butterfly clasp |
| Cartier Santos 100 | 115/115, 120/120, 125/125 |
| Cartier Santos-Dumont | 105/65, 115/75, 120/80, 125/85 |
| Cartier Tank | 100/60 to 130/90, and 110/110 |
| Citizen Zenshin | 100/60 to 130/90 |
Each product page shows the sizes for that model. If the length you need is not listed, it can be made: every strap is cut to order.
How to find your size
The quickest way is to measure a strap that already fits you on this watch: the long side from the case end to the tip, the short side from the case end to the fold at the buckle. If you close it on a middle hole, order the same two numbers.
If you have no strap to measure, send me your wrist circumference and your watch model, and I will recommend a size. The reasoning, and what changes the answer from one wrist to the next, is in how to choose the right watch strap length.
Quick reference
| Question | Answer |
|---|---|
| What does 115/75 mean? | Long side 115 mm, short side 75 mm. |
| Which side has the holes? | The long side (the first number). |
| Is the buckle included in the length? | No. |
| What does 120/120 mean? | Two equal halves, made for a butterfly clasp. |
| What if my size is not listed? | Write to me. Straps are made to order. |
