How to Measure Your Wrist Before Buying a Watch

What you really need to decide

Almost everyone starts by looking at prices and ends up making the wrong purchase. The correct approach is the reverse: first decide how you’re going to use it and how often, and only then look at the different models. Once you’ve clarified that, three or four specifications are enough to rule out 80 per cent of the range. This guide is all about exactly that: which details matter, which are just marketing hype, and how to translate them into a concrete purchasing decision.

Quartz, automatic or manual: which to choose and why

The quartz It is the most accurate and the most practical: it diverts around ±15 seconds per month, it needs nothing more than a new battery every 2–4 years and is more shock-resistant. The automatic It is powered by a wrist movement and deflects between -10 and +30 seconds a day (a COSC-certified calibre has a rate of between -4 and +6), but it is the one with a mechanical soul, a sliding seconds hand and long-term value. The manual It needs to be wound every day and is usually more delicate, which is why it’s used in dress watches. If you’re looking for accuracy, go for quartz; if you’re looking for fine watchmaking, go for an automatic.

Water resistance: what the ATM rating really means

The figure on the box does not represent the actual working depth; it is a static laboratory pressure reading. In practical terms: 3 ATM / 30 m It can withstand rain and splashes, but nothing more; 5 ATM allows you to wash your hands but not to have a shower (the hot water exceeds that pressure and the heat causes the seals to expand); 10 ATM it’s suitable for swimming; and 20 ATM / 200 m That’s the minimum for diving. If you want a proper diving watch, look for the certification ISO 6425, which can be identified by the word printed on the dial DIVER'S alongside depth.

Glass: sapphire, mineral or acrylic

The sapphire is hard 9 on the Mohs scale: Only a diamond or materials containing corundum can scratch it, which is why it’s the best choice if you’re using the watch every day. The mineral (hardness 5–6) can be scratched by sand, keys or cement, although it withstands a single impact better without chipping. The Hardlex Seiko’s is a hardened mineral, somewhere in between. The acrylic It gets scratched just by looking at it, but you can polish it at home with polish in two minutes, giving it that warm, domed look of vintage watches. An anti-reflective coating on the inside makes the dial much easier to read than one on the outside, which wears off.

Steel, titanium and coatings

The standard is the 316L steel, surgical grade, corrosion-resistant and easy to polish. The 904L (which Rolex calls Oystersteel) is slightly more corrosion-resistant and produces a denser polish, but the difference in everyday use is minimal. The titanium It weighs 40 per cent less and is hypoallergenic, making it ideal if you find the weight a problem, although it does show wear more easily. Regarding coatings: the PVD It is a thin layer that eventually wears away at the edges, whilst the DLC It is much harder and lasts for years. The gold plating on cheaper watches usually lasts between 2 and 5 years of daily use.

• Quality of materials and finishes
• Recent verified reviews (including 3–4-star reviews)
• Warranty and returns policy
• Current price compared with its historical average
• Seller's reputation
• Make sure the key features suit your needs (day-to-day use)

Power reserve – and what happens if you don’t have one

Power reserve is the length of time an automatic watch continues to run after you stop moving it: typically, this is 38–41 hours in traditional calibres, which means that if you take it off on Friday night, it will have stopped by Monday. Modern movements have extended that figure: the Powermatic 80 lasts up to 80 hours and some current calibres at 70. For several automatic watches, a rotary box It keeps them running, although this isn’t essential: leaving it switched off won’t damage the mechanism; it just means you’ll have to set the time again. What is advisable, however, is a service every 5–8 years.

Criterion	Garmin Venu 3Our choice	Invicta Pro Diver 8926OB
Ideal for	Balanced and general use	Day-to-Day Life
Strength	Value for money	Specific features
Reviews	Very positive and numerous	Positive
Approximate price	from around €80	from around €50
Recommendation	Our choice	Best alternative
View on Amazon	See price →	See price →

Straps and bracelets: the most cost-effective change

Changing the strap transforms a watch for €20–40 and is the best value-for-money upgrade there is. Measure the width between antlers (18, 20 and 22 mm are the most common) and choose according to your needs: steel for everyday use, skin for washing (never with water), rubber or FKM for sport and summer, and NATO made of nylon for a military look and quick changes. Look for pins made of quick release (quick-release) so that no tools are required. With steel bracelets, the detail that sets the good ones apart from the mediocre ones is the micro-adjustable fastening, which allows you to fine-tune the fit when your wrist swells in the heat.

How to buy a watch without being ripped off

Four things to check before paying: that the salesperson whether it is the manufacturer or an authorised distributor (on marketplaces, check who is shipping the item and who is invoicing); that the warranty is the brand’s official one and not just the seller’s; that the specifications advertised match the official profile from the manufacturer, particularly crystal and ATM models, as these are where claims are most often exaggerated; and ensure the price isn’t significantly below market value, which is a common sign of a replica. Keep the box, paperwork and receipt: with watches, these add to the value should you ever sell it.

Glossary: the terms you’ll see in the fact sheets

Lug to lug

The distance between the ends of the lugs. This determines how the watch sits on the wrist.

Power reserve

The number of hours a mechanical watch continues to run without being wound or set in motion.

Hacking

A function that stops the seconds hand when the crown is pulled out, to synchronise to the second.

ISO 6425

A standard certifying a watch as suitable for diving. It is marked ‘DIVER’S’ on the dial.

Alternations

Vibrations per hour of the movement (21,600 or 28,800 are the most common).

Fine-tuning

A clasp system that allows the size of the bracelet to be adjusted in small increments.

Super-LumiNova

Non-radioactive phosphorescent paint that absorbs light and glows in the dark.

Conclusion: the three-step decision-making process

In a nutshell: work out what you’ll actually use it for, narrow it down to the two or three features that really matter to you, and tailor your budget accordingly. With that in mind, the Garmin Venu 3 is the default choice, and the Invicta Pro Diver 8926OB is the alternative if your priorities lie elsewhere. Everything else — extra features, promotions, high-end models — is secondary if those three steps are sorted out properly.

Frequently Asked Questions

Is a quartz watch or an automatic watch better?

For accuracy and peace of mind, choose a quartz watch: ±15 seconds a month and a battery change every 2–4 years. For long-term value, choose a mechanical watch with a sliding seconds hand and automatic winding, with a tolerance of between –10 and +30 seconds a day and a service every 5–8 years.

Can I have a shower whilst wearing a 5 ATM watch?

It’s not advisable. Five atmospheres is measured under static conditions, and the shower jet generates higher pressure peaks; what’s more, the heat causes the seals to expand. For worry-free use with water, you need 10 ATM, and 20 ATM if you’re going diving.

Is sapphire glass worth it?

Yes, if the watch is going to be worn every day: with a hardness of 9 on the Mohs scale, it’s practically scratch-proof in everyday use, whereas mineral glass can be marked by sand or keys. The only advantage of mineral glass is that it absorbs a strong impact better without shattering.

Will an automatic car break down if I leave it standing?

No. Leaving it switched off won’t damage the mechanism; you’ll just need to set the time when you use it again. What it does need over the years is a service, every 5–8 years depending on use.

What width of strap do I need?

Check the distance between the lugs: 18, 20 and 22 mm will fit most watches. If your watch allows it, look for quick-release pins so you can change the strap without tools.

Should I go for the Garmin Venu 3 or the Invicta Pro Diver 8926OB?

The Garmin Venu 3 is the most well-rounded option and our default recommendation. The Invicta Pro Diver 8926OB is a good choice if your priority is everyday use. As a guide for your budget, the useful price range starts at around €50, and the best value is usually found at around €80.

By the Watch Guide Team · reviewed by

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