Lug width decides whether a strap fits your watch. Length decides whether it fits you. A strap that is too short closes on the last hole and pulls the buckle off-centre; one that is too long leaves a tail that will not stay in the keepers. The right length closes on a middle hole, keeps the buckle under your wrist, and is then forgotten.
This guide explains how strap length is described, what changes the right answer for you, and the simplest ways to choose it.
Long side and short side
A strap is made of two pieces. The long side carries the holes and the tip. The short side carries the buckle. Length is written as two numbers in millimetres, long side first: a 120/80 strap has a 120 mm long side and an 80 mm short side.
Each side is measured from the end that meets the case. The watch itself is not included, which is why the same strap wears longer on a large watch than on a small one.
These are the lengths I make most often:
| Size | Long / short side |
|---|---|
| XS | 100/60 mm |
| S | 110/70 mm |
| M | 115/75 mm |
| L | 120/80 mm |
| XL | 125/85 mm |
| XXL | 130/90 mm |
The sizes offered depend on the watch, and each product page shows the lengths for that model.
Why S, M and L are only a starting point
Size letters are convenient, but three things move the right length for the same wrist.
- The watch. The case sits between the two sides of the strap. A long case, or one with long lugs, takes up more of your wrist, so each side of the strap can be shorter. A small watch needs more strap.
- The shape of your wrist. Two wrists with the same circumference can be flat and wide or round and narrow. That changes where the buckle ends up.
- How you wear it. Some people like a watch close; others like it to move. A few millimetres either way is a matter of preference, not error.
I do not use a formula that turns a wrist measurement into a length. A formula cannot see your watch or your wrist. What works is a known reference, and a conversation when there is doubt.
The simplest way: measure a strap you like
If you already own a strap that fits this watch well, its length is the best information you can give me.
- Take the strap off, or leave it on and lay the watch flat.
- Measure the long side from the end at the case to the tip.
- Measure the short side from the end at the case to the point where the leather folds around the buckle. Do not include the buckle itself.
- Note which hole you normally use.
If you close the strap on a middle hole, order the same length. If you are on the last hole, go one size longer; on the first hole, one size shorter.
If you have no strap to measure
Wrap a soft tape measure around your wrist where you wear your watch, snug but not tight. A strip of paper marked with a pen and laid against a ruler works as well. Send me that figure with your watch model, and I will recommend a length. Because I know how each strap sits on the watch it is made for, this is more reliable than a general chart.
Straps for folding clasps
A folding clasp changes how length works, so the clasp is chosen before the strap is cut.
- A single deployant clasp uses a strap with a long and a short side, like a pin buckle strap. The clasp adds some length of its own.
- A butterfly clasp opens on both sides and sits in the middle of the strap, so both sides are the same length. The Santos 100 straps, made for the original Cartier butterfly clasp, come in 115/115, 120/120 and 125/125 mm, and the Santos has a 120/120 option.
If you are replacing a strap on a folding clasp, measure the old strap in the same way and tell me which clasp you have.
Where the buckle should sit
When the length is right, three things are true: the watch sits in the middle of the top of your wrist, the buckle sits roughly opposite it underneath, and the tip of the long side reaches through both keepers without overshooting. If the buckle is pulled towards one side of your wrist, the short side is the wrong length for you, even if the strap closes.
Bespoke proportions
Because every strap is made to order, the length is not limited to the sizes above. If you are between two sizes, or need a shorter buckle side with a longer hole side, tell me and I will cut it that way. Thickness and width at the buckle are set for the watch at the same time; the watch strap sizing guide lists them by model, and the guide to measuring lug width covers the other end of the strap.
