Lugs under 43.3 mm sit flush on your wrist; up to 47.6 mm still works but the watch will wear larger.
Orient Bambino RA-AC0M04Y30B Champagne Automatic Dress Watch 38.4mm
38.4 mm case · 44 mm L2L
Good fit
A$440.00
Orient Bambino RA-AC0M16S Peanuts 75th Anniversary Automatic Dress Watch
38.4 mm case · 44 mm L2L
Good fit
A$600.00
How to measure your wrist
Wrap a soft tape measure — or a strip of paper and a ruler, if that’s what you’ve got — around your wrist, just past the wrist bone, where a watch case actually sits when you wear one. Pull it snug, the same tension you’d want from a watch strap, not a blood pressure cuff. Note the number in centimetres and enter it above.
If you’re between two readings, measure again later in the day. Wrists swell slightly with heat and activity, so an evening measurement is usually the more honest one to size against.
Why lug-to-lug matters more than case diameter
Case diameter is the number watch marketing leads with, because it’s a single easy figure to print on a spec sheet. But diameter only measures a circle — it says nothing about how far the case actually reaches across your wrist, because lugs are rarely flush with the case edge.
Lug-to-lug is the distance between the two outermost points of the lugs, the metal tabs the strap attaches to. It’s the number that actually determines fit, because it’s the full span of the case sitting on your skin.
The gap between the two figures depends entirely on lug design, and it varies more than most buyers expect. Two watches from our own catalogue make the point: an Orient Bambino RA-AC0M02B30B has a 38 mm case, but its long, near-flat lugs push the lug-to-lug out to 44 mm — 16% larger than the case number suggests. A Seiko Prospex Turtle SRPJ35 has a considerably bigger 45 mm case, but its cushion shape curves the lugs in close, landing at 47.7 mm lug-to-lug — only 6% over. On paper the Turtle looks 7 mm bigger. On the wrist, it’s barely 4 mm bigger.
That’s why the calculator above asks for your wrist size rather than a target case diameter, and why every result shows both numbers.
Watch size chart by wrist measurement
Wrist size drives case diameter and lug-to-lug together, not independently — this table shows the same maths as the calculator above, for reference.
| Wrist (cm) | Wrist (in) | Recommended case Ø | Max lug-to-lug |
|---|---|---|---|
| 13 cm | 5.1 in | 28.6–32.6 mm | up to 36.4 mm |
| 14 cm | 5.5 in | 30.9–34.9 mm | up to 39.2 mm |
| 15 cm | 5.9 in | 33.3–37.3 mm | up to 42 mm |
| 16 cm | 6.3 in | 35.6–39.6 mm | up to 44.8 mm |
| 17 cm | 6.7 in | 38–42 mm | up to 47.6 mm |
| 18 cm | 7.1 in | 40.3–44.3 mm | up to 50.4 mm |
| 19 cm | 7.5 in | 42.7–46.7 mm | up to 53.2 mm |
| 20 cm | 7.9 in | 45–49 mm | up to 56 mm |
| 21 cm | 8.3 in | 47.4–50 mm | up to 58.8 mm |
These are balanced-fit midpoints. Diver and chronograph styles wear larger for the same wrist; dress and minimalist styles wear smaller — set your style above to see the adjusted range.
How specific models actually wear
Case diameter alone doesn’t tell you how a watch sits on your wrist. These notes are pulled from the verified and measured specs on our own product pages, not general rules of thumb.
- Orient Bambino (dress line)
- Runs long. Even the 38.4 mm case sizes reach 44 mm lug-to-lug, and the 40.5 mm versions push out to 46–46.5 mm. If your wrist is under 16 cm, look at the 38.4 mm Bambino cases specifically rather than the 40.5 mm — the lug-to-lug gap between them is bigger than the case numbers imply.
- Orient Mako / Kamasu (dive line)
- More moderate than the Bambino. A 41.8–42 mm case lands around 46.5–46.8 mm lug-to-lug — still larger than the case suggests, but a smaller jump, because the lugs angle down rather than running flat.
- Seiko 5 Sports GMT (SSK series)
- Among the truer-to-size options in the catalogue: a 42.5 mm case reaches only 46 mm lug-to-lug, a tighter ratio than most divers this size.
- Seiko Prospex Turtle
- Looks large on paper at 45 mm, but the cushion case curves the lugs in close, so it wears nearer to its diameter than a round case that size would.
- Seiko Presage Cocktail Time (compact cases, e.g. SRP837)
- Don’t judge these by the case number alone — a 33.8 mm dial still carries the watch out to 40.4 mm lug-to-lug. Small dial, not a small footprint.
- Vostok Amphibia
- Fairly average — a 41 mm case reaches 45 mm lug-to-lug, close to the typical ratio for a dive case this size.
Where a product page doesn’t have a caliper-measured lug-to-lug on file yet, the calculator above estimates it from case diameter and case shape and marks it “est.” — treat that as a close guide, not a spec.
Frequently asked questions
Is case diameter or lug-to-lug more important for fit?
Lug-to-lug. Case diameter is a useful starting point and the number most listings lead with, but it’s lug-to-lug that determines whether a watch actually overhangs your wrist. Two watches with the same diameter can differ by 5 mm or more in lug-to-lug depending on how the lugs are shaped.
My wrist measurement falls between two calculator results — which way should I go?
Round down if you prefer a slimmer, classic fit. Round up for sport and diver styles, which are designed to sit boldly rather than flush. The style selector above already applies a similar adjustment automatically.
Does strap material affect how a watch wears?
Yes. Leather and rubber straps flex around the wrist, so a slightly larger lug-to-lug is more forgiving on a leather strap than the same number would be on a rigid metal bracelet.
What does the “est.” badge next to lug-to-lug mean?
It means we haven’t measured that exact model with a caliper yet. The figure is calculated from the case diameter and case shape, which gets close but isn’t a substitute for a real measurement. We’re working through our catalogue to replace estimates with verified numbers, starting with our best-selling models.
Is a smaller case diameter always more comfortable?
Not necessarily. Case thickness and how sharply the lugs curve down matter as much as diameter — a thick, flat-lugged 38 mm watch can wear less comfortably than a slim 42 mm one.
Does this calculator work for women’s watches too?
Yes. Wrist size is wrist size — the same maths applies regardless of how a watch is marketed. Use the style and fit filters to narrow results either way.
Why does the calculator ask for style and fit preference, not just wrist size?
Because a 40 mm dress watch and a 40 mm diver wear differently on the same wrist — bezels, crowns and case shape all change how a watch reads at a given diameter. Style and fit preference adjust the recommended range to account for that.
What wrist sizes does the calculator support?
Roughly 13 cm to 23 cm (about 5.1″ to 9″). Outside that range the maths starts to extrapolate beyond what’s typical for an adult wrist, so we cap it there rather than show a number we can’t stand behind.