You've found the perfect watch, but it comes in 36mm, 39mm, or 41mm and you don't know which one to choose. This is the question we receive most often before an order, and the answer depends on a few simple criteria.
This guide gives you all the keys to making the right choice, without making a mistake.
Why case size changes everything
A case's diameter, expressed in millimeters, measures the width of the watch without including the crown. It's the first number that determines the visual impression on the wrist: a well-proportioned watch looks elegant, while a watch that's too big or too small betrays a poor choice.
But diameter alone isn't enough. Case thickness, lug length, and strap width all influence the final perception. Two 40mm watches can have very different presences on the wrist depending on their design.
How to measure your wrist correctly
First and foremost, measure your wrist. Wrap a tailor's tape measure or a piece of paper around your wrist where you usually wear your watch, just above the bone. Note the measurement in centimeters.
Here are the generally accepted correspondences in watchmaking:
| Wrist circumference | Recommended size |
|---|---|
| Less than 15 cm | 36mm or less |
| 15 to 17 cm | 36mm to 39mm |
| 17 to 19 cm | 39mm to 41mm |
| More than 19 cm | 41mm and beyond |
These benchmarks are indicative, not absolute rules. Some people with a 16 cm wrist prefer a 41mm watch for visual impact. Others with an 18 cm wrist appreciate the discreet side of a 36mm. Personal taste counts as much as morphology.
The 36mm: the classic and timeless size
A 36mm case is the historical size for dress watches. The original Rolex Datejust from 1945 measured 36mm. For decades, it was the standard for city watches.
Today, the 36mm is perfectly suited for slender wrists under 16-17 cm. It provides a discreet, elegant look that easily slips under a shirt cuff. It's also the favored size for a feminine or unisex wear.
At LSMods, the 36mm is available only on the Datejust range: classic Datejust, Arabic Dial, Wimbledon, Roman Numerals, Sunburst, Who Cares, Galaxy, and Heritage. It's our most versatile format for slender wrists.
The 39mm and 39.5mm: the universal compromise
The 39mm is currently the most popular size in watchmaking for men and women. It adapts to the vast majority of wrists, from 15 to 18 cm, without ever appearing too small or too imposing.
This is the size that works in all situations: in the office with a formal outfit, on weekends with jeans, or for an evening out. The 39mm is neither shocking nor unnoticeable. It's the choice for versatility.
In our workshop, the 39mm is available across the entire Datejust range, which offers both 36mm and 39mm sizes depending on the models. The Land Dweller, on the other hand, adopts a slightly different 39.5mm format, which gives it a slightly more assertive presence while remaining within the proportions of a sporty city watch.
The 40mm: the size of sports watches
The 40mm is the standard for dive watches and sports watches. It's at this size that dials become truly readable at a glance, rotating bezels make sense, and brushed steel fully expresses itself.
A 40mm case fits well on wrists starting from 16-17 cm. On a thinner wrist, it might appear slightly bulky depending on the case thickness and lug length.
In the LSMods range, the 40mm equips the Submariner and the Marine Master. These two dive watches, inspired by great professional timepieces, naturally adopt this format, which corresponds to the sporty and robust aesthetic of these models.
The 41mm: a bold presence
The 41mm is the size of modern sport-chic watches. This is the format adopted today by the original Audemars Piguet Royal Oak and many high-end contemporary watches. A 41mm watch assumes a visible and assertive presence on the wrist.
To be comfortable with a 41mm, a wrist of at least 17 cm is recommended. On a thinner wrist, the watch may slightly overhang the sides, which is not necessarily a flaw but changes the visual balance.
At LSMods, the 41mm equips the Royal Oak and the Nautilus in their classic versions. These two models have an integrated bracelet that visually softens the size of the case: the bracelet extends the case seamlessly, which gives a more fluid impression than a round watch of the same diameter with a separate bracelet.
The effect of the integrated bracelet on perceived size
This is a point many people overlook. On models with integrated bracelets like the Royal Oak and Nautilus, the case and bracelet form a continuous whole. The eye glides from the bracelet to the case without interruption, which makes the perceived size softer than on a watch with a separate bracelet.
In practice, a 41mm Royal Oak may seem less imposing on some wrists than a 40mm Submariner with an Oyster bracelet, because the case-bracelet transition is different. This is a factor to consider, especially if you are hesitating between several models.
Summary of sizes in the LSMods range
| Model | Size | Style | Recommended wrist |
|---|---|---|---|
| Datejust | 36mm or 39mm | Classic, dressy | From 14 cm (36mm), from 15 cm (39mm) |
| Land Dweller | 39.5mm | Sport-city | From 16 cm |
| Submariner | 40mm | Diving, sport | From 16-17 cm |
| Marine Master | 40mm | Diving, robust | From 16-17 cm |
| Royal Oak | 41mm | Sport-chic, integrated | From 17 cm |
| Nautilus | 41mm | Sport-chic, integrated | From 17 cm |
Some practical benchmarks before ordering
If you're hesitating between two sizes for the Datejust, choose the 36mm if your wrist is less than 16 cm or if you're looking for discretion and elegance. Choose the 39mm beyond that, or if you want a more visible presence for everyday wear.
If you're torn between the Datejust 39mm and the Submariner 40mm, the difference is mostly in style rather than size. The Datejust is a dress watch, while the Submariner is a sport watch. The one-millimeter difference will be barely noticeable.
If you're hesitating between the Submariner 40mm and the Royal Oak 41mm, consider the integrated bracelet effect mentioned above. The Royal Oak may appear more worn despite its slightly larger diameter.
When in doubt, check the lug-to-lug measurement, which is often more revealing than the diameter alone. A watch with short lugs fits smaller wrists better than a watch with long lugs, even at the same diameter.
Your questions about watch size
What watch size for a 17 cm wrist? A 17 cm wrist is versatile. You'll be comfortable with a 39mm, 40mm, or 41mm depending on the desired style. A 36mm will also work, but will give a more discreet result. Across our range, all sizes are suitable for a 17 cm wrist.
Is 41mm too big for a 16 cm wrist? Not necessarily. On models with integrated bracelets like the Royal Oak and Nautilus LSMods, the 41mm can look great on a 16 cm wrist thanks to the visual continuity of the bracelet. It's still a matter of personal taste.
Does the Datejust come in other sizes than 36 and 39mm in SeikoMod? No. In our range, the Datejust is only available in 36mm and 39mm. These are the two formats that correspond to the classic aesthetic of this model.
How do I know which size corresponds to my reference photos? Look at photos of your favorite watches on Instagram or Pinterest and check the diameter in the model description. Then compare it with your wrist circumference. If you see a result you like on someone's wrist, check if their morphology is similar to yours.
Does size affect comfort? Yes, but mainly through case thickness and lug length, not just diameter. All our models have a thickness of 13mm, making them wearable daily without discomfort under a cuff.
Can I return a watch if the size is not suitable? Yes. We offer a 14-day satisfaction or money-back guarantee from the date of receipt. If the size does not meet your expectations upon receipt, please contact us.
Trust your instincts
Size guides are benchmarks, not rules. Watchmaking is above all a matter of personal taste. Some people love wearing oversized watches, others prefer discreet models on large wrists. What matters is that you love what you see on your wrist every morning.
If you have any doubts, do not hesitate to contact us before ordering. We know every model in our range and can guide you in a few exchanges.
Browse our complete collection or use our configurator to view available options.
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