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Seiko watch · Presage · automatic

Seiko SSA405

The Seiko SSA405 measures 40.5 mm across, 47.5 mm lug to lug, and 11.8 mm thick, with 20 mm lugs. It fits wrists from ~17 cm (flat-fit estimate).

Sources checked · How we source numbers
Case
40.5 mm1
Lug to lug
47.5 mm1
Thickness
11.8 mm1
Lug width
20 mm1
Seiko SSA405: size drawingSeiko SSA405, round case, top and side view to scale: case diameter 40.5 mm, lug to lug 47.5 mm, lug width 20 mm, thickness 11.8 mm. Bezel, dial and crown size are schematic.lug width 20Ø 40.5lug to lug 47.5TOPthickness 11.8SIDE
Seiko SSA405, top and side, to scaleDrawing from data, not a photo · mm

Seiko SSA405 specifications

Case diameter
40.5 mm1
Lug to lug
47.5 mm1
Thickness
11.8 mm1
Lug width
20 mm120 mm watches
Weight
70 g1
Crystal
Box-shaped Hardlex1
Water resistance
5 bar (50 m)1
Movement
Seiko 4R381 · automaticSeiko 4R38 specs
Battery
none: the Seiko 4R38 is automatic
Years made
start not published
Case code
not in our data yet

On your wrist

The verdict compares the lug to lug with the flat top of your wrist. Balanced from ~17 cm, past the edges below ~15 cm.

= 6.7 in

Balanced on a 17 cm wrist: the 47.5 mm lug to lug covers 87% of an estimated 54.8 mm flat top.

Flat top = circumference ÷ 3.1, a community convention, not a measurement of your arm. Compact ≤ 0.75 of the flat top, balanced ≤ 0.89, at the edge ≤ 1. Compare more watches in the watch size calculator.

Seiko SSA405: wrist fitSeiko SSA405 on a wrist, top view to scale. lug to lug 47.5 mm. Wrist 170 mm, estimated flat width 54.8 mm (circumference / 3.1). Ratio 0.87: balanced.wrist, flat topwrist flat ≈ 54.8lug to lug 47.5Balanced · 47.5 / 54.8 = 0.87estimate: wrist 170 / 3.1 = 54.8 flatcompactbalancededgeoverhang0.750.891
Seiko SSA405 on a 17 cm wristDrawing from data, not a photo · mm

Actual size on your screen

Calibrate once with a bank card and the drawing shows the Seiko SSA405 at 1:1, next to a millimetre ruler.

1:1 · not calibrated: sizes are approximate
Seiko SSA405: size drawingSeiko SSA405, round case, top and side view to scale: case diameter 40.5 mm, lug to lug 47.5 mm, lug width 20 mm, thickness 11.8 mm. Bezel, dial and crown size are schematic.lug width 20Ø 40.5lug to lug 47.5TOPthickness 11.8SIDE
Drawing from data, not a photo · mm
01020304050

Seiko SSA405 strap size

Lug width 20 mm1: a 20 mm strap with 20 mm spring bars fits between the lugs. 62 other models take 20 mm.

Attachment: not published in our sources.

Find your strap length in the watch strap size tool, with the Seiko SSA405 filled in.

On a bracelet? How to remove watch links to size it to your wrist.

20 mm strap: strap diagramTwo-piece strap laid flat (20 mm strap). Lug width 20 mm. Short piece — (unknown), long piece — (unknown). Buckle, keepers and holes are schematic.short —long —lug 20lug 20strap length —20 mm strap
20 mm at the lugs; lengths depend on your wristDrawing from data, not a photo · mm

Movement: Seiko 4R38

The Seiko SSA405 runs on the Seiko 4R38, an automatic movement.

Beat rate
21,600 bph2
Power reserve
41 h2
Accuracy
−35 to +45 s/day2
Hacking seconds
Yes2
Hand winding
Yes2

Battery

none: the Seiko 4R38 is automatic

A mechanical watch has no cell to replace; it needs a service instead.

Same size as the Seiko SSA405

The models nearest to the Seiko SSA405 in case width and lug to lug, drawn over it to scale; below, every model within 1 mm of its 47.5 mm.

Size comparison: Seiko SSA405, Seiko SRPG03, Seiko SRPG07, Seiko SRPG09Top-view outlines to scale on one centre. A Seiko SSA405: Ø 40.5, L2L 47.5, lug 20, T 11.8. B Seiko SRPG03: Ø 40.8, L2L 47, lug 20, T 12 (vs A: Ø +0.3 L2L −0.5 lug 0 T +0.2). C Seiko SRPG07: Ø 40.8, L2L 47, lug 20, T 12 (vs A: Ø +0.3 L2L −0.5 lug 0 T +0.2). D Seiko SRPG09: Ø 40.8, L2L 47, lug 20, T 12 (vs A: Ø +0.3 L2L −0.5 lug 0 T +0.2).A Ø 40.5B Ø 40.8C Ø 40.8D Ø 40.8B L2L 47C L2L 47D L2L 47A L2L 47.5A Seiko SSA405Ø 40.5 · L2L 47.5 · lug 20 · T 11.8B Seiko SRPG03Ø 40.8 · L2L 47 · lug 20 · T 12vs A: Ø +0.3 L2L −0.5 lug 0 T +0.2C Seiko SRPG07Ø 40.8 · L2L 47 · lug 20 · T 12vs A: Ø +0.3 L2L −0.5 lug 0 T +0.2D Seiko SRPG09Ø 40.8 · L2L 47 · lug 20 · T 12vs A: Ø +0.3 L2L −0.5 lug 0 T +0.2
A Seiko SSA405 and the 3 nearest in size, on one centre, to scaleDrawing from data, not a photo · mm

Nearest in size

  1. ASeiko SSA405this watch
  2. BSeiko SRPG03W +0.3 · L2L −0.5 · T +0.2 mm
  3. CSeiko SRPG07W +0.3 · L2L −0.5 · T +0.2 mm
  4. DSeiko SRPG09W +0.3 · L2L −0.5 · T +0.2 mm

Differences against A in mm: W case width, L2L lug to lug, T thickness. Nearest by width and length together, from the published sizes.

Same published case dimensions (3)Seiko SRPD37, Seiko SRPE15, Seiko SRPE19

Seiko SSA405 questions

How big is the Seiko SSA405?

The Seiko SSA405 measures 40.5 mm across, 47.5 mm lug to lug, 11.8 mm thick, 70 g.

Will the Seiko SSA405 fit a 7-inch wrist?

Balanced: the Seiko SSA405's 47.5 mm lug to lug takes 83% of the ~57.4 mm flat top of a 7-inch (17.8 cm) wrist. By the same estimate (circumference ÷ 3.1) it sits balanced from about 17 cm and overhangs the flat top on wrists under about 15 cm.

Does the Seiko SSA405 need a battery?

No. The Seiko SSA405 has no cell to replace: a wound mainspring drives its automatic Seiko 4R38.

What movement is in the Seiko SSA405?

The Seiko SSA405 runs on the Seiko 4R38, an automatic movement.

What strap size does the Seiko SSA405 take?

The Seiko SSA405 measures 20 mm between the lugs, so it takes a 20 mm strap with 20 mm spring bars. 62 other models in our base share that width.

Find the strap length for your wrist and the Seiko SSA405 in the watch strap size tool.

More Seiko watches

Sources

Documents checked · Report a wrong number

  1. 1Seiko Watch Corporation — SSA405J1 product page (Presage), seikowatches.com global-en · html · read
  2. 2Seiko Watch Corporation — Mechanical watch instructions, Cal. 4R35/4R36/4R37/4R38/4R71/4R72/4R39 (EN) · pdf · read