Reference Guide · Updated September 20, 2026 · Guía de Relojes Team

Casio and digital watches: why they’re still going from strength to strength

From the indestructible G-Shock to vintage steel models: which Casio watches are worth buying and why they last for decades.

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.

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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.

Which watch is right for each occasion?

The classic rule still holds true: the more formal the occasion, the more understated and simple the watch should be. For suit, a 36–40 mm case, a slim profile that fits under the wrist, a clean dial and a leather strap. For office and diary, an elegant sports watch measuring 38–41 mm with a steel bracelet covers all the bases. For sport and water, a 200-metre diver’s watch or a rugged digital watch. And for to travel, a GMT watch lets you keep track of two time zones at a glance. If you’re only going to own one watch, a 39–40 mm three-hand model with 10 ATM water resistance and an interchangeable bracelet is the most versatile option available.

Value and depreciation: which watches hold their value

Almost all watches are an expense, not an investment, and it’s best to buy them with that in mind. That said, there are clear patterns: models from brands with a rich history and limited production runs retain their value better on the second-hand market, whilst fashion brands lose between a 60 and 80 per cent as soon as they leave the shop. Affordable watches with an established reputation (the classics from Seiko, Casio or Orient) rarely fall much below the initial price range because their starting price is already low. The paperwork, the box and the condition of the strap affect the selling price more than people realise.

Luminescence: Super-LumiNova and LumiBrite

Modern luminescent paint is not radioactive: it is a phosphorescent material that absorbs light and gradually releases it. Super-LumiNova (Switzerland) and LumiBrite (Seiko) are the models, with variants such as the bluish BGW9 or the greenish C3, which is the one that shines the brightest. What makes the difference in practice is not the paint brand but the layer thickness: that’s why a €150 Seiko can outshine a €1,500 Swiss watch. With diving watches, check that the bezel at 12 o’clock and the minute hand – which is the one that counts underwater – are also luminescent.

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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 that it is the brand’s official specification in Spain and not just that of the seller; 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.

All Casio products and digital watches (23)

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Frequently asked questions about Casio watches

How much should a good first watch cost?

In the €100–200 price range, there are options that will last for years, featuring tried-and-tested automatic movements or maintenance-free solar-powered quartz watches. Moving up to the €400–700 price range buys you a better finish, sapphire crystal and movements with a longer power reserve, but not greater reliability.

Do sundials need maintenance?

Virtually none. The cell lasts between 10 and 20 years and the capacitor can be replaced; under normal lighting conditions, even artificial light, they remain charged and retain a reserve of power for months in the dark.

What does it mean for a watch to be ISO 6425-compliant?

It has passed the standardised tests for diving watches, not just the pressure test. It can be recognised by the word ‘DIVER’S’ printed on the dial next to the depth marking; without this marking, it is a water-resistant watch but not a certified diver’s watch.

How often should a mechanical watch be serviced?

Every 5–8 years under normal use, to clean and lubricate the movement and replace the gaskets. For diving watches, it is advisable to check the water resistance every 1–2 years if the watch is actually used in water.

How much do I need to spend on a Casio watch?

It depends on how you plan to use it: there are good options in the entry-level range, as well as advanced models that are only worth the extra cost if you’re going to make the most of their features. Check the criteria in this guide, work out how you’ll actually use it, and compare the current price on Amazon before making a decision.

Other guides from the Watch Guide

Automatic watches Diving watches Men's watches Women's watches Smartwatch or traditional watch Sundials Watch guides

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