How to Read Watch Specifications: A Beginner’s Guide

Nowadays, you can buy watches online — but when you open their description, often a flood of terms like caliber, jewels, power reserve, hacking, and more jumps out at you. For many people, it feels like a foreign language. In this article, I will explain in simple and clear terms what these specifications mean, so you don’t get lost when buying watches.

Caliber
Caliber is the designation of the movement inside the watch. Every movement has its number or name.

For example:

• ETA 2824-2 → Swiss mechanical movement

• Miyota 8215 → Japanese mechanical movement

• Seiko 7S26 → legendary movement in Seiko 5

• Citizen E111 → Eco-Drive quartz movement

Caliber determines:

• Accuracy of the watch

• Lifespan

• Service cost

• Functions (complications)

Jewels (Bearing Stones)
Mechanical watches often state “21 jewels” or similar. These are synthetic rubies that serve as bearings for gears. They reduce friction and prolong the movement’s life.

More jewels don’t automatically mean higher quality. For simple three-hand watches, 17–25 jewels suffice.

Power Reserve
Indicates how long the watch will run if you’re not wearing or winding it. For example:

• 38 hours → typical for cheaper movements

• 80 hours → modern movements (e.g., Tissot Powermatic 80)

• 120 hours → high-end watches

For automatic watches, the longer the power reserve, the more convenient the usage.

Hacking
Means that when you pull out the crown, the second hand stops. This lets you set the watch exactly to the second.

Examples:

• Seiko 7S26 → no hacking

• Seiko 4R36 → has hacking

Manual Wind
Mechanical watches can be:

• Manual wind → you have to wind the crown daily

• Automatic → wind themselves by wrist movement

Some automatics also allow manual winding, which is handy if the watch hasn’t been worn for a while.

Frequency
Given in vibrations per hour (vph) or hertz (Hz). For example:

• 21,600 vph = 3 Hz → second hand moves less smoothly

• 28,800 vph = 4 Hz → smoother second hand

Higher frequency means smoother seconds hand movement and better accuracy.

Chronometer
Watches labeled chronometer have passed official precision tests (e.g., COSC in Switzerland). They are extremely accurate:

• Deviation max. −4 to +6 seconds per day

Chronometers are more expensive but very high quality.

Chronograph
Not to be confused with chronometer! A chronograph means the watch has a stopwatch function to measure short time intervals.

You’ll recognize it by extra subdials on the watch face.

GMT
Allows tracking a second time zone. The watch has a fourth hand showing time on a 24-hour scale.

Examples:

• Rolex GMT-Master II

• Seiko 5 Sports GMT

WR / ATM / BAR
Indicates water resistance:

• WR 30M → hand washing only

• WR 50M → shower, short immersion

• WR 100M → swimming

• WR 200M → diving

Note: 30M does NOT mean you can dive 30 meters deep!

Case Diameter
Measured in millimeters. Standard sizes:

• Men’s watches → 38–42 mm

• Women’s watches → 28–36 mm

Lug-to-Lug
Distance between the top and bottom strap attachment points. Determines how big the watch looks on the wrist. For example:

• 48 mm lug-to-lug → fits larger wrists

• 44 mm lug-to-lug → fits smaller wrists

Thickness
Watches can be:

• Ultra-thin → up to 8 mm, great for suits

• Regular → 10–14 mm

• Dive watches → 15–17 mm

Sapphire Crystal
The most durable glass. Scratch-resistant. If the watch doesn’t say “sapphire,” it’s often just mineral glass.

Super-LumiNova
A luminous material that glows in the dark. Watches with quality Super-LumiNova glow for several hours after exposure to light.

Deployant Clasp
A special clasp that:

• Protects the strap from wear

• Makes the watch easier to put on

Skeleton
Watches where you can see the movement through the dial or case back. Especially appreciated by those who enjoy watching mechanical workings.

Screw-down Crown
A screw-down crown increases water resistance. You have to unscrew it before adjusting.

Movement
Another word for the watch’s mechanism. Can be labeled as:

• Automatic Movement → self-winding movement

• Quartz Movement → battery-powered movement

Anti-Magnetic
Watches resistant to magnetic fields. Important mainly for mechanical watches.

Common Myths About Specifications

• “More jewels means a better watch.” → Not necessarily. Above 25 jewels is often marketing.

• “30M water resistance means diving.” → No. It’s fine for rain only.

• “Skeleton watches are always luxury.” → There are cheap skeletons too.

• “All watches have hacking.” → No. Cheap movements often lack it.

• “Quartz watches need no servicing.” → Quartz also needs occasional service for seals or battery.

FAQ – Frequently Asked Questions

Which is better – automatic or quartz?
It depends on what you want. Quartz is more accurate and cheaper. Automatic has the soul of mechanics.

What does hacking mean?
That the second hand stops when setting the watch, allowing precise time adjustment.

How many jewels should a quality watch have?
17–25 jewels are sufficient.

Are all GMT watches expensive?
No. For example, Seiko 5 Sports GMT starts around 10,000 CZK.

Do I need sapphire crystal?
If you want a scratch-resistant watch, definitely yes.

What is lug-to-lug?
The length of the watch from one lug end to the other. Determines how large it appears on the wrist.