Watch Size for Wrist Calculator: Case Size & Lug-to-Lug

As a widely used guideline, a 7-inch (17.8 cm) wrist suits a watch case of about 40 to 44 mm, and a 6.5-inch (16.5 cm) wrist suits about 38 to 42 mm. Enter your wrist below to get a watch size for your wrist, a maximum lug-to-lug length and a strap length; treat every figure as a rule of thumb, not a standard.

Wrist circumferenceUnitinchescentimetres

Your conversion appears here. The full chart is below.

Watch size by wrist (guideline)

Wrist	Wrist (cm)	Case diameter	Max lug-to-lug (approx.)
under 6"	< 15.2 cm	34–38 mm	≤ 43 mm
6" – 6.5"	15.2–16.5 cm	36–40 mm	43–46 mm
6.5" – 7"	16.5–17.8 cm	38–42 mm	46–50 mm
7" – 7.5"	17.8–19.1 cm	40–44 mm	50–53 mm
7.5" – 8"	19.1–20.3 cm	42–46 mm	53–57 mm
8" and up	20.3+ cm	44–48 mm	57+ mm

How to measure your wrist for a watch

1. Use a soft tape measure. If you do not have one, a thin strip of paper or a piece of string and a ruler work too.
2. Wrap it round the wrist you wear a watch on, at the spot where the watch sits, usually just next to the wrist bone.
3. Keep it snug against the skin without squeezing. A watch strap is fastened with a little room, and the calculator allows for that in the strap length.
4. If you are using paper or string, mark where it overlaps, then lay it flat and measure up to the mark with the ruler.
5. Measure twice and use the average. Enter the figure in inches or centimetres.

Why lug-to-lug matters more than diameter

Case diameter is the width of the watch across the dial, usually measured without the crown. It is the number most shops quote, but it only tells half the story.

Lug-to-lug is the distance from the tip of the top lugs to the tip of the bottom lugs, the four small arms that hold the strap. It runs along your arm, so it decides whether the watch sits on top of your wrist or hangs over the edges. Two 40 mm watches can wear very differently: one with short, curved lugs looks compact, while one with long, straight lugs looks much bigger.

The top of the wrist is fairly flat, and the calculator estimates that flat area as about 28% of your wrist’s circumference. It then uses that figure as your maximum lug-to-lug. For a 7-inch wrist, that is about 50 mm. If a watch’s lugs are longer than your figure, they are likely to overhang, whatever its diameter.

Case size bands and strap length

The calculator places your wrist in one of six bands, from under 6 inches (34–38 mm) up to 8 inches and over (44–48 mm). The bands overlap on purpose, because taste matters: a dress watch often looks right towards the small end of your range, and a sports or dive watch towards the large end.

A wrist that sits right on a boundary can wear either band. A wrist of exactly 7 inches is placed in the 7–7.5 inch band (40–44 mm), but one just under 7 inches gets 38–42 mm, so anything from 38 to 44 mm is reasonable around that size.

Strap lengths are given as two numbers, such as 120/75 mm, for the long piece and the buckle piece. The calculator suggests short straps (about 110/70 mm) below 6.5 inches, regular straps (about 120/75 mm) from 6.5 to 7.5 inches, and long straps (about 130/80 mm) above that. These are typical values, so check the maker’s figures.

Quick answers

• 6-inch wrist: 36–40 mm case, lug-to-lug up to about 43 mm
• 6.5-inch wrist: 38–42 mm case, lug-to-lug up to about 46 mm
• 7-inch wrist: 40–44 mm case, lug-to-lug up to about 50 mm
• 7.5-inch wrist: 42–46 mm case, lug-to-lug up to about 53 mm
• 8-inch wrist: 44–48 mm case, lug-to-lug up to about 57 mm
• 16 cm wrist: 36–40 mm case, lug-to-lug up to about 45 mm
• 18 cm wrist: 40–44 mm case, lug-to-lug up to about 50 mm

FAQs

What size watch suits a 7-inch wrist?

Around 40 to 44 mm in the calculator, and 38 mm also works if your wrist is a touch under 7 inches. Look for a lug-to-lug length of about 50 mm or less.

Is a 40 mm watch too small for a man?

Not by this guideline. A 40 mm case falls inside the suggested range for wrists from 6 to 7.5 inches. Wrist size matters here, not whether the wearer is a man or a woman.

What size watch suits a small wrist?

For a wrist under 6 inches (15.2 cm), the guideline is 34 to 38 mm, with lugs that stay under roughly 43 mm. Thinner cases and short, curved lugs help a watch sit flat.

Where do I find a watch’s lug-to-lug length?

Many makers list it on the product page or specification sheet. If they don’t, you can measure it from tip to tip with a ruler, or ask the seller.

Does case thickness change how big a watch looks?

It can. A thick case sits higher off the wrist and may look larger from the side, even when the diameter is within your range. It is worth checking if you often wear shirts with close cuffs.

If you are buying a ring as well, the ring size converter works the same way, and our Journal has longer guides on choosing a watch. All of our converters are in the size guide.

The case sizes come from a widely used rule of thumb that matches wrist circumference bands to case diameters. It is a guideline, not a standard, and personal taste still counts. Maximum lug-to-lug is estimated as 28% of wrist circumference, our approximation of the flat top of the wrist, rounded to the nearest millimetre. Strap lengths are typical values.