Parts of a watch, explained
A labelled guide to the parts of a watch — case, lugs, bezel, crystal, crown, dial, indices, hands, strap and the movement inside — and what each one does.
In this guide
Every watch, from a plastic field watch to a gold dress piece, is built from the same short list of parts. Learn their names and two things happen: watch reviews suddenly make sense, and you can start designing your own. If you want to make a watch, this is the vocabulary you'll use at every step.
Here's the outside of a watch, labelled.
The case
The case is the metal body that holds everything else. It protects the movement from dust, knocks and water, and it sets the watch's size and shape. Case size is usually quoted as the diameter in millimetres, not counting the crown — most men's watches today are 38–42 mm, most women's 28–36 mm.
Cases come in far more shapes than round: tonneau, cushion, tank, octagon and oval all have their own history. See watch case shapes for the full tour, and watch case materials for steel, titanium, gold and the rest.
The lugs
The lugs are the four horns that stick out from the case at the top and bottom. A small spring bar runs between each pair and holds the strap. Two measurements matter here:
- Lug width — the gap between the lugs, which tells you what width of strap fits (20 mm is the most common).
- Lug-to-lug — the length from the tip of the top lugs to the tip of the bottom ones. This, more than diameter, decides whether a watch fits your wrist.
The bezel
The bezel is the ring around the crystal. On a dress watch it's a thin polished band. On a diver it's a rotating ring with a 60-minute scale that only turns one way — so an accidental bump can only make you think you have less air left, never more. Bezels can also be fluted (cut with fine ridges), thin and flat, or set with gemstones, each one hand-set in its own seat.
The crystal
The crystal is the clear cover over the dial. Three materials are common:
| Crystal | Pros | Cons |
|---|---|---|
| Sapphire | Almost scratch-proof; found on most mechanical watches today | Can shatter from a hard knock; more expensive |
| Mineral glass | Cheap and fairly tough | Scratches more easily |
| Acrylic (Hesalite) | Warm vintage look; scratches polish out | Scratches easily |
The crown
The crown is the knurled knob on the side of the case, usually at 3 o'clock. On a mechanical watch it does two or three jobs:
- In its normal position, turning it winds the mainspring.
- Pulled out one step (on watches with a date), it sets the date.
- Pulled out fully, it sets the time.
Crowns vary with the watch's job: pilot watches have big "onion" crowns you can grip in flight gloves, and divers often have screw-down crowns to keep water out. More in how to wind a mechanical watch and how to set one.
The caseback
The caseback closes the back of the case. It's either solid steel (often engraved) or a display caseback with a sapphire window, so you can watch the movement's balance wheel swing and the rotor spin.
The dial
The dial is the face of the watch, and it does more for the look than any other part. It's defined by its colour, its finish — sunburst, linen, enamel, guilloché, mother of pearl, fumé — and the markings printed or fixed onto it. The dial finishes guide covers each one.
Many dials also carry subdials or windows for extra functions, like the date window at 3 o'clock in the diagram above.
Indices and minute track
The indices (or hour markers) mark the hours: batons, dots, Roman numerals, Arabic numerals, diamonds, or a California mix of Roman and Arabic. Around the edge, a minute track — often a "railway" of fine ticks — helps you read the exact minute. See watch indices and numerals.
The hands
Most watches have three hands:
- The short hour hand.
- The long minute hand.
- The thin seconds hand, often in an accent colour. On a mechanical watch it moves in tiny steps — five to ten a second — which is why it looks like a smooth sweep.
Some watches move the seconds to a small subdial at 6 o'clock ("small seconds"), and some add a fourth hand, like a GMT hand for a second time zone. Hand shapes have names — Dauphine, Breguet, Mercedes, syringe and more — covered in watch hand styles.
Strap, bracelet and clasp
The strap (leather, rubber, fabric) or bracelet (metal links or mesh) holds the watch on your wrist. A strap closes with a buckle or a folding deployant clasp; a bracelet closes with a clasp, often with micro-adjustment holes. Changing the strap is the cheapest way to change a watch's character — see straps and bracelets.
Inside the watch: the movement
Behind the dial sits the movement (or calibre) — the engine that keeps time. A mechanical movement has five main parts, working in a chain:
| Part | What it does |
|---|---|
| Mainspring | A coiled ribbon of metal in a drum called the barrel. Winding coils it tighter; it stores the energy. |
| Gear train | A series of wheels that carries the energy from the barrel toward the escapement and drives the hands. |
| Escapement | The escape wheel and pallet fork release the energy in tiny, even steps — the "tick". |
| Balance wheel | Swings back and forth at a steady rate, controlled by a hairspring. It's the watch's timekeeper. |
| Rotor (automatics only) | A half-moon weight that swings as you move and winds the mainspring for you. |
You'll also hear about jewels — synthetic rubies used as low-friction bearings for the wheels. A simple hand-wound movement typically has 17; automatics often have 21 to 25. For how all this fits together, read how a mechanical watch works.
Put the parts together in Mecha Watch
Once you know the parts, the fun part is choosing them. Mecha Watch is built around exactly this list. You pick a case (11 shapes), a metal, a bezel, a dial colour and finish, indices, a minute track, hour, minute and seconds hands, a movement, complications and a strap — then put your own name on the dial and watch the pieces assemble.
Flip the finished watch over and you'll see the movement beating through the caseback. Turn the crown and feel each click as the mainspring winds. That's why the name works so well said out loud: Mecha Watch — make a watch.
Frequently asked questions
What are the main parts of a watch called?
On the outside: the case, lugs, bezel, crystal, crown, caseback, dial, indices, hands and strap or bracelet. Inside a mechanical watch: the movement, made up of the mainspring, gear train, escapement, balance wheel and, in automatics, the rotor.
What is the knob on the side of a watch called?
It's the crown. On a mechanical watch you turn it to wind the mainspring, and pull it out to set the date and time.
What is the ring around a watch face called?
The bezel. It can be a plain polished ring, a fluted ring, a gem-set ring or a rotating dive bezel with a minute scale.
What are the lugs on a watch?
The lugs are the four projections at the top and bottom of the case that hold the strap or bracelet, usually with spring bars. Lug width sets the strap size; lug-to-lug length decides how the watch fits your wrist.
What is the face of a watch called?
The dial. The hour markers on it are called indices, and small extra dials within it are called subdials.
What is the engine of a watch called?
The movement, also called the calibre. It can be mechanical (hand-wound or automatic) or quartz (battery-powered).