Seiko Watches Under 40mm

4 Seiko models in the 0–40mm range, actually measuring 38.4mm to 39.9mm. Compact sizing that suits smaller wrists and dressier looks.

Thickness barely moves across the group — 11.2mm to 12mm — so these wear much alike under a cuff.

Under 40mm 40–44mm 44mm & Larger

Which of these fits your wrist?

Flat wrist width55.0mm

Roughly a 14.7cm wrist circumference — the measurement a tape gives you. Compared against lug-to-lug where we have it, case width otherwise.

4 of 4 models sit on this wrist without the lugs hanging over the edge.

Model	Your Fit	Width	Thickness	Shape
Mechanical Stainless Stainless Steel / Black / Bracelet	Roomy8.3mm clear	38.4mm	11.2mm	circular
Mechanical Stainless Stainless Steel / Silver / Bracelet	Roomy8.3mm clear	38.4mm	11.2mm	circular
Mechanical Alpinist Stainless Steel / Green / Strap	Balanced7.8mm clear	39.5mm	12mm	circular
Prospex Diver SLA017J1 Stainless Steel / Black	Balanced7.6mm clear	39.9mm	—	circular

Same size, other brands

The middle of this group sits around 39mm. These are the closest matches we hold from other brands — useful when the size is right but the Seiko isn't.