What is an ebauche movement?

An ebauche is an unfinished base movement supplied by a specialist maker such as ETA or Sellita, which brands then finish, regulate and case. Many watches share the same ebauche under different brand names, which is why calibre numbers are a useful reference.

What does bph mean and why does it matter?

Bph is beats per hour, the rate at which the balance oscillates. Dividing by 3600 gives the frequency in Hz, so 28,800 bph equals 4 Hz. Higher beat rates generally improve positional accuracy and produce a smoother-looking seconds hand.

Why does an ETA 2824 appear in so many different watches?

The ETA 2824-2 is a reliable, affordable, widely produced automatic, so countless brands used it as their base movement. After Swatch Group restricted supply, Sellita's near-identical SW200 became the common drop-in replacement.

Are Japanese movements lower quality than Swiss ones?

Not inherently. Japanese makers like Seiko and Miyota produce everything from budget automatics to the high-grade Grand Seiko 9S calibres that meet or beat Swiss chronometer standards. Quality depends on the specific calibre and finishing, not the country.

Does this tool need an internet connection?

No. The reference data and the bph conversion run entirely in your browser. Nothing is fetched, uploaded or stored.

What is the Watch Movement Reference?

Reference table of major watch calibre numbers with manufacturer, type, beat rate (bph/Hz), power reserve and jewels for Swiss and Japanese mechanical movements, plus a live filter. It runs free in your browser on Gera Tools, with nothing uploaded.

Watch Movement Reference

Name: Watch Movement Reference
Creator: Gera Tools
License: https://creativecommons.org/licenses/by/4.0/

A quick map of the movements inside your watch

Mechanical watches are usually built on a relatively small set of base calibres that get shared, finished and rebranded across the industry. This reference lists the major Swiss and Japanese movements you are most likely to meet, with their manufacturer, type, beat rate, power reserve and jewel count, plus a filter to find a specific calibre fast.

How it works

Each entry lists the calibre number, its maker and origin, the movement type and the headline specifications. The beat rate is shown in beats per hour (bph) alongside its frequency in hertz:

Hz        = bph / 3600
ticks/sec = Hz * 2

So a 28,800 bph movement oscillates at 4 Hz and produces 8 audible ticks per second, while a vintage 18,000 bph calibre runs at 2.5 Hz with a slower, more stepped seconds hand. Power reserve is the running time from a full mainspring, and the jewel count indicates the synthetic-ruby bearings that reduce friction at high-wear pivots.

Why calibre numbers matter when buying a watch

Many watch brands market movements under proprietary names without disclosing the base ebauche, which makes it hard to compare value or availability of service parts. Knowing that a given watch uses, say, an ETA 2892 or a Miyota 9039 tells you more than the brand name alone: it tells you the expected service interval, whether watchmakers will have familiar tools, and whether genuine replacement parts will be easy to source decades from now.

This matters most in the mid-market, where some brands charge premium prices for movements that are widely available, while others charge similar prices for in-house calibres that offer genuinely proprietary value. Cross-referencing a calibre number in this reference quickly reveals who made it and what to expect.

Common movements and what to know about each

ETA 2824-2 / Sellita SW200. These two automatics are nearly interchangeable: same dimensions, same function, and widely serviced. After Swatch Group restricted ETA supply to outside brands, Sellita’s SW200 became the common replacement across dozens of Swiss brands. Both beat at 28,800 bph and typically have a 38-hour power reserve. If a watch advertises a “Swiss automatic” movement without naming the calibre, these are the two most likely candidates in the $300–$1,500 price range.

ETA / Valjoux 7750. The default automatic chronograph movement for much of the Swiss industry. Its distinctive layout puts sub-dials at 6, 9, and 12 o’clock. The vertical clutch design is reliable and serviceable, and the movement appears in everything from entry-level sport chronographs to well-regarded tool watches. It beats at 28,800 bph with roughly a 42-hour reserve.

Seiko NH35 / NH36. Seiko’s workhorse automatics, found in everything from affordable Seiko 5 models to many microbrand watches that use the calibre for its reliability and low cost. The NH35 beats at 21,600 bph — a slower, lower-cost oscillation that is perfectly adequate for daily wear but produces a more stepped seconds sweep than higher-frequency movements. The NH36 adds a hacking seconds function.

Miyota 9039 / 9015. Miyota (the movement division of Citizen) produces high-quality automatics that punch well above their price. The 9039 in particular is used by several respected microbrands because it lacks a date wheel (keeping the dial clean), beats at 28,800 bph, and is finished to a higher standard than most movements at its cost. It can occasionally exhibit “pallet flutter” — a slight irregularity in seconds ticking — that some owners notice.

Grand Seiko 9S65. Seiko’s high-grade automatic calibres, found in Grand Seiko watches, are regulated to tolerances that equal or exceed the COSC chronometer standard. The 9S65 beats at 28,800 bph with a 72-hour power reserve. These movements receive individual quality control and finishing far beyond the brand’s volume calibres.

Tips and notes

An ETA 2824-2 and a Sellita SW200 are functionally interchangeable — useful to know when a brand is vague about its movement.
The Valjoux/ETA 7750 is the default automatic chronograph; recognise it by its 6/9/12 sub-dial layout.
A higher bph is not automatically “better” — it can mean more wear and oil demand, which is why some high-end makers deliberately stay at 3 Hz.
Grand Seiko’s 9S65 and Rolex’s 3135 show that both Japan and Switzerland produce serially-made movements regulated tighter than the COSC chronometer standard.
Jewel count is a specification from an era when each jewel had to be individually set. Modern movements typically use 21–25 jewels for a standard automatic; more jewels do not automatically mean higher quality.