Audemars Piguet's 38mm Royal Oak Chronograph receives its most meaningful update with the new in-house calibre 6401, the Manufacture's first compact in-house chronograph movement. This development addresses a technical gap that persisted even after the 41mm variant adopted Calibre 4401 in 2022. Where larger Royal Oak Chronographs transitioned to proprietary architecture, the 38mm continued with the modified Frédéric Piguet 1185 ébauche—capable but sourced—rebranded as Calibre 2385.
Case dimensions remain at 38mm in diameter with minimal profile increase to 11.1mm, preserving the reference’s appeal to wrists unable to comfortably accommodate 41mm architecture. Gérald Genta's 1972 design language remains unchanged. Three launch variants: a stainless steel with a blue dial reference 26450ST.OO.1356ST.01, an 18K pink gold with a grey ruthenium dial reference 26450OR.OO.1356OR.01, and an 18K pink gold with a sand gold-toned dial and diamond-set bezel reference 26450OR.ZZ.1356OR.01.
The Movement
Calibre 6401 represents five years of development focused on miniaturization without functional compromise, and, hopefully, the ongoing issues with calibre 4400 were not transferred into this new calibre. The 27mm-diameter movement integrates column-wheel chronograph architecture with a vertical clutch via a patented system, reducing the component count while eliminating mechanical play. Beating at 28,800 vph, the calibre delivers 55 hours of power reserve—extending from the previous 40 hours—while adding just 0.2mm to movement thickness at 5.7mm.
The movement's architecture becomes visible through a sapphire case back, now standard across the 38mm Chronograph range. Côtes de Genève, polished bevels, and an openworked rotor demonstrate finishing standards applied across case materials and price points. A perfect size for a watch positioned to appeal to collectors seeking compact proportions and those requiring gender-neutral sizing. Calibre 6401 will migrate into additional collections throughout 2026, with Royal Oak Offshore references specifically mentioned.
Summary & Price
For collectors who found 41mm Royal Oak Chronographs dimensionally excessive yet resisted acquiring movements assembled from third-party ébauches, Calibre 6401 resolves a tension that existed since 2019. The 38mm format now offers complete manufacture integration at a size that accommodates diverse wrist proportions.
Sticker Price USD 43,000 for steel; USD 84,500 for pink gold; and USD 91,600 for pink gold with diamond-set bezel. For more info on Audemars Piguet click here.
