What should my first automatic watch have?

A first automatic should have a sapphire or at least hardened crystal, a 100 meter water resistance rating, a movement that stops the seconds hand for setting and winds at the crown, and a lug to lug span that sits inside the flat of your wrist. Add a screw-down crown if it will get wet, an even lug width, a caliber with parts available where you live, and a warranty from a seller who will honor it.

Every item is available for a few hundred dollars, allowing for the way local retail moves with tax, import duty and market, and all of it is printed on the spec sheet before you pay.

Crystal: sapphire, or hardened at minimum

The crystal is the part you will damage first, because it meets doorframes, countertops and car keys. Synthetic sapphire rates 9 on the Mohs hardness scale, just below diamond. Ordinary mineral glass rates roughly 5 to 6, below the quartz grit in everyday dust at 7. That is why mineral collects a haze of fine scratches within a year of daily wear while sapphire still looks new.

If the budget will not stretch to sapphire, a hardened mineral crystal such as the chemically strengthened glass Seiko and Citizen use is the acceptable floor: better than plain mineral, less brittle than sapphire under impact. What you should not accept is untreated mineral glass. See our comparison of crystal materials.

Water resistance: 100 meters is the practical floor

Ratings come from a static pressure test, not a depth you can descend to, and nobody swims statically. Swinging an arm through water or diving off a pool edge briefly generates pressures well above the marked figure's still-water equivalent, which is why the industry discounts ratings in practice.

Under that discount, a 30 meter watch survives handwashing and a 50 meter watch survives rain. A 100 meter rating is the first that covers swimming and showering without you thinking about it, and for a first watch you want to stop thinking about it. Our water resistance checker maps ratings to activities, and whether 100 meters is enough covers the edge cases. The rating also ages: gaskets compress, so budget a pressure test every couple of years if the watch gets wet often.

The movement: hacking, hand-winding, and parts you can get

Two features cost nothing extra and are worth insisting on. Hacking stops the seconds hand when you pull the crown out, the only way to set a watch to the second against a reference clock. Hand-winding starts a stopped watch at the crown rather than by shaking it. Some budget calibers offer neither, so check.

The more important question is whether the movement can be repaired near you. Widely supplied calibers such as the Seiko NH series, Citizen's Miyota 8 and 9 series, the ETA 2824 and the Sellita SW200 are stocked by parts suppliers worldwide and familiar to independent watchmakers in most cities. A proprietary caliber may be excellent and still leave you shipping the watch overseas, or find parts restricted to the brand's own network.

Fit: lug to lug first, lug width second

Case diameter is the number everyone quotes and the least useful one. What decides whether a watch sits properly is lug to lug, the tip-to-tip length of the case, because that dimension either fits the flat top of your wrist or hangs off it. A 40 mm watch with long straight lugs wears larger than a 42 mm one with short curved lugs.

Measure the flat span across the top of your wrist and keep the lug to lug under it. As a rough guide, a 16.5 cm (6.5 inch) wrist is comfortable to about 47 mm lug to lug, a 19 cm (7.5 inch) wrist to about 52 mm. Our watch size calculator works it out from your measurements, and what lug to lug distance means explains the measurement.

Then check the lug width. Even numbers, particularly 18, 20 and 22 mm, have enormous strap selection at every price. Odd widths such as 19 or 21 mm, and proprietary fittings that take only the brand's own straps, lock you out of the cheapest way to change how a watch looks.

The checklist

On that last row: an authorized dealer is what makes the manufacturer's warranty enforceable. Gray market sellers often substitute their own coverage, worth as much as the company behind it. The written manufacturer warranty is the contract wherever you live, and the statutory rights that sit on top of it differ from one country to the next, so check what your own law adds before you rely on it. Read the terms before checkout, and price a service in with our cost of ownership calculator.

What matters less than buyers think

• In-house movements. An in-house caliber says the brand made it, not that it runs better. Supplied movements are proven across millions of units and easier to repair. See in-house versus third party.
• Exhibition casebacks. Pleasant on a decorated movement, unremarkable on a plain one, and one more sealed joint to keep dry.
• High beat rates. A 28,800 vibrations per hour movement has finer theoretical resolution than a 21,600 one and no reliable accuracy advantage in daily wear. Regulation matters more than frequency.
• Antimagnetic claims. The formal standard requires resistance to a 4,800 A/m field, which covers ordinary life. Claims of many thousands of gauss address people who work near MRI machines, not commuters.

Spend the attention you save on the crystal, the rating, the fit and the seller. Those four decide how the watch feels to own. Buying your first mechanical watch covers the purchase itself.