Calibre, power reserve, 20 bar: the watch world loves its jargon. This watch knowledge translates the most important technical terms into plain words, so you can read spec sheets like a pro. Each term stands for a criterion you will find again in our catalogue and in the watch comparison.
A mechanical watch that winds itself while worn: a rotor swings with every movement of your hand and tensions the mainspring. No battery, but regular movement or winding is needed. For the detailed comparison with quartz, see the guide Automatic vs. Quartz.
Battery-powered drive in which an electrically oscillating quartz crystal sets the beat. Quartz watches are considerably more accurate than mechanical watches, usually slimmer and low-maintenance. Depending on the model, the battery needs changing every two to five years.
The original form of the mechanical watch: the spring is tensioned by hand via the crown every day. Manual-winding movements are often slimmer than automatic movements because the rotor is omitted. Many wearers appreciate the daily winding as a ritual.
Quartz watch with a solar cell in the dial that converts light into energy and stores it in a rechargeable cell. Fully charged, such watches run for many months even in the dark. Citizen calls the technology Eco-Drive, Casio Tough Solar; a battery change is practically eliminated.
The exact type designation of a watch movement, such as Seiko 4R36 or Sellita SW200-1. The calibre reveals the origin, functions and often the quality level of a movement. In our catalogue it appears for every watch in the technical dossier.
The time a mechanical watch keeps running after the last winding without being worn. 38 to 42 hours is classic; modern movements such as the Powermatic 80 reach 80 hours. For people who rotate between watches, a high power reserve is a real gain in convenience.
A protected designation for movements whose rate accuracy has been tested by the Swiss testing body COSC: a deviation of at most minus 4 to plus 6 seconds per day. Not to be confused with the chronograph, which denotes a stopwatch function. Tudor and Omega have many movements certified.
A watch with an integrated stopwatch function, readable via additional subdials, the registers. It is started and stopped with pushers beside the crown. The most famous example is the Omega Speedmaster Moonwatch, the watch of the moon landings.
A fourth hand shows a second time zone on a 24-hour scale, often combined with a two-tone bezel for day and night. Practical for frequent travellers and anyone who works with other time zones. The name comes from Greenwich Mean Time.
The ring around the watch crystal. On dive watches it rotates in one direction only and measures dive time; on chronographs it often carries a tachymeter scale. Materials range from aluminium through steel to scratch-resistant ceramic.
The figure in metres or bar is a laboratory test pressure, not a diving depth: 3 bar (30 m) only means splash-proof, 5 bar withstands hand washing and rain, from 10 bar (100 m) swimming is possible, and from 20 bar (200 m) with a screw-down crown diving too. More in the guide to the best dive watches.
The three usual watch crystals compared by hardness: sapphire crystal is extremely scratch-resistant and the standard in the higher class, mineral glass is a solid middle ground, acrylic glass (also Hesalite or Plexi) is soft but polishable and shatter-resistant. Seiko's Hardlex is a hardened mineral glass.
The distance between the outer ends of the lugs, measured across the case. This measurement decides more than the diameter whether a watch fits your wrist. How to measure correctly is shown in the watch size guide.
Glow-in-the-dark coating on hands and indices that makes the watch readable in the dark. Modern compounds such as Super-LumiNova or Seiko's LumiBrite charge up in light and are free of radioactivity. The quality and duration of the glow differ markedly between the classes.
A movement that the watchmaker develops and manufactures itself, instead of buying it from specialists such as ETA or Sellita. In-house movements are regarded as proof of technical independence, while bought-in movements are proven and inexpensive to service. Both have their place.
The major overhaul of a mechanical watch: the movement is taken apart, cleaned, re-oiled and regulated, and the seals are replaced. It is recommended roughly every five to ten years. The cost depends heavily on brand and movement.
A motorised device that turns automatic watches at intervals and so keeps them wound when they are not being worn. 650 to 800 turns per day in both directions are usual, but a winder is not a must. Our accessory sister site collects the documented values per calibre in the TPD table.
The manufacturer's recommended retail price is the list price that the market orients itself by. Our guide prices are derived from it and are deliberately marked as a rough guide, because street prices can differ considerably. You always see the current price in the linked shop.