What length watch strap do I need?

Width and length are two different questions

Lug width decides whether a strap goes into the watch at all. Length decides whether it closes comfortably once it is on. The database answers the first for every reference. The second depends on you, and it is the one nobody publishes, because one length has to serve everyone.

Your watch is part of the circle

The case sits in the circle around your wrist, so it uses up length that the strap then does not have to cover. Between a small case and a large one the difference is not small.

• 27 mmsmall end
• 40 mmmiddle
• 46 mmlarge end

Across the 39,283 watches in the database that carry a case diameter, the middle of the range is 40 mm and most sit between 27 and 46 mm. That is 19 mm from one end to the other: close to two centimetres of wrist, taken up or given back by the watch alone. The same strap, on the same person, closes on a different hole depending on which watch it is carrying.

Will a standard strap close on you?

Enter your wrist and the diameter of the watch. The holes on a standard strap run from 55 mm to 95 mm along the long side, so the answer is exact rather than approximate.

What it is working out

Everything sits in one circle: the watch, the short piece, and however much of the long piece it takes to reach the buckle. So the length that has to close around you is your wrist minus the watch, minus the 75 mm short side. The watch counts for its lug-to-lug, tip to tip, not for its case diameter: those are different numbers, and on a 40 mm case the lug-to-lug is usually 46 to 48.

wrist − watch (lug to lug) − 75 mm = how far along the 115 mm long side the buckle has to close

A 7.5 inch wrist is 191 mm. On a 40 mm watch that leaves 76 mm to cover on a long side that is 115 mm: comfortably inside it. The same wrist on a 27 mm case has to reach 89 mm instead, closer to the end, because the small watch gives back less of the circle.

The holes themselves are not in any database. There are 7 of them, the first 55 mm from the lug and the last 20 mm from the tip, measured at our bench. That is what turns the arithmetic above into a hole number instead of a yes or a no.

How to know before you order

You do not need a tape measure for this one. Look at the strap you are wearing now, on the watch you would put the new one on, and see which hole you close it on.

1. A hole somewhere in the middle. The standard length reaches you comfortably. Order by width and stop thinking about it.
2. The last hole, or past comfortable. You are at the end of what a standard strap gives. A longer piece is not sold separately: it is cut.
3. The first hole, with a long tail left over. The strap is too long for you. The tail flaps, the keeper does the work, and the watch rides around the wrist.

When the answer is a strap made for you

If you close on the last hole, or on the first, the standard length is not reaching you. Another brand may cut a centimetre longer or shorter, but it is still one fixed length chosen without knowing your wrist, so the odds of it landing where you need it are the same odds you just played. A strap made to measure is cut to your wrist and to the watch it will carry, so the buckle sits where it should instead of where the length allows.

Other questions

• Does lug width change within the same watch family?67.7% of watch families use more than one lug width. Knowing the family is not enough.67.7%
• What is the most common lug width?20 mm, on 38.8% of measured watches. What the rest of the distribution looks like.20 mm
• Can a watch have an odd lug width like 21 mm?One watch in six takes an odd size. 21 mm is not a rounding error.16.3%
• Why will no strap fit my watch?6.1% of watches have no lug width at all. Here is what to do instead.2,632

All questions →