An automatic watch is a mechanical watch that winds itself from the motion of your wrist. There is no battery; a rotor spins as you move, tightening a mainspring that drives the movement. Many people find that satisfying in a way a quartz watch is not, but a first automatic is also easy to get wrong. Here is what to weigh up before you buy.

1. Understand what you are buying

A mechanical movement is less accurate than quartz. A good entry-level automatic gains or loses somewhere between -20 and +40 seconds a day; a regulated or chronometer-grade movement does better. If you will be bothered by resetting the time every week or two, a quartz or solar watch may suit you better. Automatics also stop if left unworn for a day or two (the power reserve is usually 38 to 72 hours), so you will set the time and date more often than you expect.

2. Choose a proven movement

The movement matters more than the logo on the dial. Widely used calibres from Seiko (NH35/4R, 6R), Miyota (8215, 9015), Sellita (SW200) and ETA (2824) have parts everywhere and any competent watchmaker can service them. A watch built around one of these will be cheaper to own over a decade than an obscure movement. Look for “hacking” (the seconds hand stops when you pull the crown, so you can set the time precisely) and hand-winding, both of which make daily life easier.

3. Get the size right

Automatics are thicker than quartz watches because of the rotor, typically 11 to 14 mm. That thickness is what you will notice under a shirt cuff, not the diameter. Measure your wrist and check the lug-to-lug length on the listing: if it is longer than the flat part of your wrist, the watch will overhang and feel larger than its diameter suggests. Most first-time buyers are happiest between 38 and 41 mm.

4. Be realistic about water resistance

A dress automatic rated 3 ATM should stay away from water altogether. If you want to swim, look for 10 ATM or more, ideally with a screw-down crown. Whatever the rating, never operate the crown under water and have the seals checked whenever the watch is opened.

5. Crystal, bracelet and dial

Sapphire crystal resists scratches far better than mineral glass and is worth paying a little extra for. A solid-link bracelet with a milled clasp feels better than folded links and costs more to make. On the dial, applied markers and a clean date window are signs of care; avoid anything that is hard to read at a glance.

6. Plan for servicing

An automatic should be serviced every 5 to 7 years. That costs money, so budget for it, and favour movements that any independent watchmaker can work on. A watch with a common calibre, sapphire crystal and sensible size will still be a pleasure to wear long after the novelty has worn off – and that, rather than the spec sheet, is the point of a first automatic.