What is the difference between a mechanical watch and a quartz watch?
A mechanical watch keeps time with a wound spring driving a train of moving parts, while a quartz watch keeps time with a crystal oscillator that vibrates steadily when voltage is applied. The mechanical needs winding or wrist motion; the quartz depends on an electrical supply. Accuracy and upkeep differ accordingly.
The short version is this: a mechanical watch is a machine made of springs and gears, and a quartz watch is an electronic device that uses a vibrating crystal as its timekeeping standard. Everything else that people say about the two types - accuracy, servicing, feel on the wrist - flows from that one difference in how the movement counts time.
[1][2]How each movement actually keeps time
In a quartz watch, the core is a crystal oscillator. Seiko's own customer service pages explain that a crystal cut to a fixed shape generates a steady vibration when voltage is applied to it, and that vibration serves as the standard of timekeeping accuracy. Seiko brought the first commercially viable quartz watch to market on 25 December 1969, the Seiko Quartz Astron. Its quartz frequency was 8192 Hz, which Seiko notes was one-fourth of the frequency used today. One visible feature of that watch - a second hand that moves in individual steps, driven by an open step motor - went on to become a symbol of quartz watches generally.
[1]A mechanical watch, by contrast, counts time mechanically. Seiko's description of its automatic 6R20 calibre gives a concrete picture of what that involves: 208 parts, 29 jewels, 28,800 beats per hour, and a mainspring that stores energy and delivers a power reserve of more than 45 hours. The movement also has hand-winding capability, and an engraved rotor that winds the watch. An automatic is simply a mechanical whose rotor uses the motion of your wrist to keep the spring wound, so the two terms are not rivals - automatic is a subset of mechanical.
[2]Accuracy, in plain figures
Seiko publishes a daily accuracy figure for the 6R20 of minus 15 to plus 25 seconds per day. That is the honest scale of mechanical timekeeping for this calibre: seconds per day, not seconds per month. Quartz accuracy is described differently - by the steadiness of the crystal's vibration rather than a published daily drift band - so the two are not directly comparable from the figures given here. What can be said is that the crystal oscillator was adopted precisely because its accuracy had been demonstrated as excellent, which is why the technology was pursued for watches in the first place.
[1][2]A worked example: two watches, one drawer
Suppose, hypothetically, you own both types and leave each in a drawer for a weekend. The mechanical will run down. The 6R20's power reserve is quoted at more than 45 hours, so by Monday morning it has stopped and needs winding or wearing to restart. The quartz watch has no spring to run down; its timekeeping continues as long as its electrical supply holds. But the reverse scenario matters too: the mechanical, once wound, needs no electrical supply at all, whereas the quartz watch's accuracy depends entirely on voltage being applied to the crystal. Each type has a dependency the other does not have.
[1][2]What the specifications do not settle
Two common claims need careful handling. First, battery life and replacement intervals: Seiko's pages do not state how long a quartz watch's battery lasts or what a replacement costs, so no figure can responsibly be given here - check the manufacturer's specification for the exact reference you are buying. Second, mechanical service intervals: the movement descriptions cover construction but not how often a mechanical watch should be serviced. Treat any universal rule of thumb you read elsewhere as a claim to verify with the maker or a qualified service centre, not a settled fact.
[1][2]A checklist for choosing
- If you want the second hand to sweep and the watch to be a purely mechanical object with no electrical dependency, look at mechanical and automatic calibres.
- If published daily accuracy matters to you, ask the manufacturer for the specific calibre's rating - Seiko, for instance, states minus 15 to plus 25 seconds a day for the 6R20.
- If you dislike winding a stopped watch after time in a drawer, note the power reserve figure before buying; more than 45 hours is quoted for the 6R20.
- If you are comparing prices, match the full model reference and barcode, since a single collection name can cover watches with different movements.
- Confirm condition, warranty, delivery and returns with the retailer before purchase, and confirm today's price - recorded prices are dated observations, not live quotes.
Next step: when you shortlist a specific watch, find its exact calibre or movement reference in the specification, then look up that calibre's published accuracy and power reserve on the manufacturer's own customer service pages. That single check tells you more about how the watch will behave day to day than the mechanical-versus-quartz label alone.
[1][2]Sources and dates
- https://www.seikowatches.com/uk-en/customerservice/knowledge/quartz-knowledge · accessed 2026-10-18
- https://www.seikowatches.com/uk-en/customerservice/knowledge/mechanical-knowledge · accessed 2026-10-18