Buying a Watch Online: Movements, Water Resistance and Warranties

A watch is easy to choose on looks alone, but the specifications decide how you live with it: whether it needs a battery, whether you can swim in it, and whether the maker will repair it if something goes wrong. Here's how to read a watch listing.

Movement types

The movement is the mechanism that keeps time.

Mechanical watches (automatic and manual) are generally less accurate than quartz and benefit from periodic servicing. The listing may give a power reserve, which is how long the watch runs when fully wound without further winding.

Water resistance ratings explained

This is the most misunderstood figure on a watch listing. Ratings are given in metres, bar or ATM, and they come from a pressure test in a laboratory. They are not the depth you can safely dive to.

A few things reduce water resistance in real life:

• Seals age. Gaskets dry out over the years, so resistance should be retested periodically, and after a battery change.
• The crown must be pushed in or screwed down. Some watches have screw-down crowns for extra protection.
• Hot water and steam (showers, saunas, hot tubs) are hard on seals even when the rating is high.
• Don't press buttons underwater unless the watch is designed for it.

Size and strap fit

Watch sizes are given in millimetres.

• Case diameter is the width of the case, usually excluding the crown.
• Lug-to-lug is the length from the top to the bottom lug. It decides whether the watch overhangs your wrist, and is often more useful than the diameter.
• Thickness matters if you wear shirts with fitted cuffs.
• Lug width (such as 18, 20 or 22 mm) tells you which replacement straps will fit.

Measure your wrist with a soft tape, or a strip of paper and a ruler, and compare it with the strap length or bracelet size in the listing. Metal bracelets usually need links removing to fit. Check whether the seller sizes the bracelet for you, whether the tool is included, and whether sizing affects your right to return the watch.

Authorised dealers, grey market and pre-owned

Where you buy can matter as much as what you buy.

• Authorised dealers are appointed by the brand to sell its watches. You get the full manufacturer's warranty and the usual paperwork.
• Grey-market sellers sell genuine, new watches obtained outside the brand's official network, often at lower prices. The trade-off is that the manufacturer's warranty may not apply, and the seller provides its own warranty instead. Read exactly what that covers and who carries out repairs.
• Pre-owned sellers offer used watches. Look for clear photos of the actual watch, its service history, and whether the original box and papers are included.

Counterfeits are a real risk, particularly for well-known designs at unusually low prices. Use our guide on checking whether an online store is legit, and be wary of reviews that seem too uniform; our guide on how to spot fake reviews can help.

Reading the warranty

Before you buy, check:

1. Who provides the warranty: the manufacturer, or the seller.
2. How long it lasts, and whether it's valid in your country.
3. What it excludes. Straps, crystals, batteries and water damage are commonly excluded.
4. What you need to claim: often the dated warranty card and proof of purchase. Keep both.

If you're buying from another country, warranty service may mean posting the watch abroad. Our international shipping and customs guide covers duties and delivery, and it's worth comparing prices across stores once those costs are added in.