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Choosing an automatic

An automatic watch winds itself from the movement of your wrist through a weighted rotor. It needs no battery, but it runs less accurately than quartz and needs a service every several years.

Entry movement accuracy
rated within about 20 to 45 seconds a day
Power reserve
about 40 to 80 hours off the wrist, by movement

Inside an automatic (self-winding) watch, a half-moon rotor turns as your wrist moves and winds the mainspring. The mainspring releases its energy through the gear train and the escapement, and the balance wheel swings at a steady rate, commonly 21,600 or 28,800 beats per hour. Most automatics can also be wound with the crown; a few entry movements cannot.

Compared with quartz, an automatic is less accurate and costs more to keep up. Entry movements such as the Seiko 4R and NH series or the Miyota 8 series are rated within roughly 20 to 45 seconds a day, while chronometer certified movements (COSC) are tested to -4 to +6 seconds a day. Position, temperature and how fully wound the watch is all move the daily rate.

Plan for a service every five to ten years, depending on the maker's advice and how the watch runs. On an entry movement a full service can cost close to a replacement movement, so many owners of affordable automatics have the movement swapped instead. Also check whether the watch hacks (the seconds hand stops when you pull the crown to set the time) and whether it hand-winds: both make daily use easier.

  1. Wrist motionYour arm moves.
  2. RotorA half-moon weight spins on its axle.
  3. Reversing wheelsTurn both swing directions into winding.
  4. Mainspring barrelStores the energy as a coiled spring.
  5. Gear trainCarries the power to the hands.
  6. Escape wheelReleased one tooth at a time.
  7. Pallet forkLocks and unlocks the escape wheel.
  8. Balance wheelSwings back and forth at a steady rate.
Wrist motion turns the rotor, which winds the mainspring. The escapement lets that power out in even steps to the hands.

Common mistakes

  • Expecting quartz accuracy and returning a healthy watch for running a few seconds a day fast.
  • Buying a watch that does not hand-wind when you plan to rotate between several watches.
  • Leaving the service cost out when comparing an automatic with a quartz watch.

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