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.

Watch Movement Reference

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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.

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.