Audemars Piguet Royal Oak Offshore Chronograph: 26405CE, 26400 and 26237 Compared

The Audemars Piguet Royal Oak Offshore chronograph is the brand's sports chronograph built on the Royal Oak octagonal bezel, and the references most buyers compare are the 42mm steel 26237, the 44mm 26400 family and the 44mm ceramic 26405CE. All three are self-winding and use the same modular movement, so the real differences are case size, case material and dial design. This guide explains how to read the numbers and which one suits which wrist. Bizak & Co. is a sourcing desk: every watch mentioned here is sourced on request, not held as stock.

Last reviewed on October 28, 2026 by Filip Biczak. Specifications are summarized from manufacturer-adjacent and dealer references and can vary by exact suffix, so confirm the full reference of any unit before you commit. Sources: WristCheck, Offshore 44mm vs 43mm and Life of a WIS, 26400SO hands-on.

What is the Royal Oak Offshore chronograph?

It is the chronograph that started the Offshore line in 1993 and has been reinterpreted in larger cases ever since. The Offshore keeps the Royal Oak's eight-screw octagonal bezel and integrated design but adds a thicker, more muscular case, chunky pushers and a Mega Tapisserie dial. In this guide, "Offshore Selfwinding Chronograph" means the three-register model, not the diver, the Tourbillon or the limited-edition variants, which have their own guides.

How do the 26405CE, 26400 and 26237 compare?

The 26237 is the 42mm steel model, the 26400 is the 44mm model that carried the line through the 2010s, and the 26405CE is the 44mm all-ceramic update. Sources agree they share the caliber 3126/3840 modular chronograph; the table keeps to the points that are consistent across references.

Dealer listings for the 26405CE give 100m water resistance, but that rests on retailer pages rather than an official sheet, so check the unit's paperwork.

How do you read an Offshore chronograph reference?

The first five characters name the model family and the letters after them name the case materials. In 26405CE, "26405" is the model number and "CE" signals ceramic; in 26400SO, the letters point to steel and ceramic, and in 26400RO to pink gold and ceramic. The block after the dots, such as OO.A056CA.01, covers the strap or bracelet, the dial and the variant. Two watches with the same first block can have different dials, so always ask for the full string and photographs of the actual unit.

What is the difference between 42mm and 44mm?

The 42mm 26237 wears more compactly, while the 44mm references have more wrist presence and a bolder, thicker profile. Offshore watches wear large for their stated diameter because of the thick case and the integrated lugs, so a 44mm can look dominant on a smaller wrist. If you have a wrist under roughly 7 inches, try a 42mm or a 43mm modern chronograph before settling on 44mm. Our guide to choosing case size by wrist covers fit in more detail.

Is the 26405CE ceramic better than steel?

Ceramic resists scratches far better than steel and keeps its finish, but it is lighter in feel and can chip on a hard impact. Steel is easier to service and refinish, which matters for a watch you wear daily. Ceramic colorways such as the 26405CE with a smoked green dial, green ceramic bezel and black ceramic case are more distinctive; steel is the more traditional choice.

Which movement powers these chronographs?

All three run the caliber 3126/3840, a self-winding base movement with a chronograph module on top. It beats at 21,600 vibrations per hour. The generation that replaced the 44mm line, launched around 2021, moved to the in-house caliber 4401 with a flyback chronograph, a 4 Hz beat and a 70-hour reserve, and a 43mm case. If a flyback chronograph matters to you, shop that newer generation instead; if you prefer the larger, older design, the references above are the target.

Which Offshore chronograph should you choose?

Choose the 26237 for a compact steel look, the 26400 family for the classic 44mm presence in the metal you prefer, and the 26405CE if you want a ceramic case with a modern colorway. Browse the Audemars Piguet Royal Oak collection and the wider Audemars Piguet range to compare current looks. For adjacent models, read our guides to the Royal Oak Offshore 26470 and the Royal Oak Concept.

How do you buy one without overpaying?

Confirm the full reference, the dial and the paperwork first, then compare it against several recent listings rather than a single asking price. Discontinued references trade as pre-owned, so condition, the service history and whether the box and papers are present move the number more than the year. A sourcing request lets us find a matching unit and confirm its details before you commit.

Quick answers

What is the difference between the 26405CE and the 26400?

The 26405CE is the all-ceramic 44mm version, while 26400 is the broader 44mm family that includes steel, gold and mixed-material suffixes. Both use the same caliber 3126/3840.

Is the 26237 a 42mm watch?

Yes. The 26237ST is a 42mm stainless steel Offshore chronograph, issued as a re-edition of the original 1993 design.

What movement does the 26405CE use?

Dealer and review sources list the caliber 3126/3840, a self-winding modular chronograph running at 21,600 vibrations per hour.

Does the Offshore chronograph have a flyback function?

The 3126/3840 generation does not; the newer 43mm generation with caliber 4401 does.

Can Bizak & Co. source an Offshore chronograph?

Yes. We source specific units on request and confirm the reference, photographs and terms before you commit.

Related reading: Royal Oak Offshore 26470 guide and Royal Oak Concept guide.

Get your Offshore sourced

Tell us the model, size, dial and bracelet preference, whether you want new or pre-owned, and your budget and timing, through our sourcing enquiry form. We confirm the specific watch, photographs and final price before you commit.