Skip to content
WatchtheDetails

Seiko watch · 5 Sports · automatic

Seiko SRPD51

The Seiko SRPD51 measures 42.5 mm across, 46 mm lug to lug, and 13.4 mm thick, with 22 mm lugs. It fits wrists from ~16.5 cm (flat-fit estimate).

Sources checked · How we source numbers
Case
42.5 mm1
Lug to lug
46 mm1
Thickness
13.4 mm1
Lug width
22 mm1
Seiko SRPD51: size drawingSeiko SRPD51, round case, top and side view to scale: case diameter 42.5 mm, lug to lug 46 mm, lug width 22 mm, thickness 13.4 mm, rotating bezel. Bezel, dial and crown size are schematic.lug width 22Ø 42.5lug to lug 46TOPthickness 13.4SIDE
Seiko SRPD51, top and side, to scaleDrawing from data, not a photo · mm

Seiko SRPD51 specifications

Case diameter
42.5 mm1
Lug to lug
46 mm1
Thickness
13.4 mm1
Lug width
22 mm122 mm watches
Weight
170 g1
Crystal
Hardlex1
Water resistance
10 bar (100 m)1
Movement
Seiko 4R361 · automaticSeiko 4R36 specs
Battery
none: the Seiko 4R36 is automatic
Years made
start not published
Case code
not in our data yet
Bezel
unidirectional rotating1
Line
5 Sports1

On your wrist

The verdict compares the lug to lug with the flat top of your wrist. Balanced from ~16.5 cm, past the edges below ~14.5 cm.

= 6.7 in

Balanced on a 17 cm wrist: the 46 mm lug to lug covers 84% 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 SRPD51: wrist fitSeiko SRPD51 on a wrist, top view to scale. lug to lug 46 mm. Wrist 170 mm, estimated flat width 54.8 mm (circumference / 3.1). Ratio 0.84: balanced.wrist, flat topwrist flat ≈ 54.8lug to lug 46Balanced · 46 / 54.8 = 0.84estimate: wrist 170 / 3.1 = 54.8 flatcompactbalancededgeoverhang0.750.891
Seiko SRPD51 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 SRPD51 at 1:1, next to a millimetre ruler.

1:1 · not calibrated: sizes are approximate
Seiko SRPD51: size drawingSeiko SRPD51, round case, top and side view to scale: case diameter 42.5 mm, lug to lug 46 mm, lug width 22 mm, thickness 13.4 mm, rotating bezel. Bezel, dial and crown size are schematic.lug width 22Ø 42.5lug to lug 46TOPthickness 13.4SIDE
Drawing from data, not a photo · mm
01020304050

Seiko SRPD51 strap size

Lug width 22 mm1: a 22 mm strap with 22 mm spring bars fits between the lugs. 45 other models take 22 mm.

Attachment: not published in our sources.

Find your strap length in the watch strap size tool, with the Seiko SRPD51 filled in.

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

22 mm strap: strap diagramTwo-piece strap laid flat (22 mm strap). Lug width 22 mm. Short piece — (unknown), long piece — (unknown). Buckle, keepers and holes are schematic.short —long —lug 22lug 22strap length —22 mm strap
22 mm at the lugs; lengths depend on your wristDrawing from data, not a photo · mm

Movement: Seiko 4R36

The Seiko SRPD51 runs on the Seiko 4R36, an automatic movement. 47 other models in our base use it.

Beat rate
21,600 bph2
Power reserve
41 h2
2 sources disagree; show every value
  • manufacturer 41 h2
  • secondary source 40, 41 h4
Jewels
242
Accuracy
−35 to +45 s/day3
Hacking seconds
Yes2
Hand winding
Yes2

Battery

none: the Seiko 4R36 is automatic

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

Same size as the Seiko SRPD51

The models nearest to the Seiko SRPD51 in case width and lug to lug, drawn over it to scale; below, every model within 1 mm of its 46 mm.

Size comparison: Seiko SRPD51, Seiko SSC957, Islander ISL-94, Seiko SARX055Top-view outlines to scale on one centre. A Seiko SRPD51: Ø 42.5, L2L 46, lug 22, T 13.4. B Seiko SSC957: Ø 41.4, L2L 45.9, lug 21, T 13 (vs A: Ø −1.1 L2L −0.1 lug −1 T −0.4). C Islander ISL-94: Ø 42, L2L 47, lug —, T 13 (vs A: Ø −0.5 L2L +1 T −0.4). D Seiko SARX055: Ø 40.8, L2L 46.2, lug —, T 11 (vs A: Ø −1.7 L2L +0.2 T −2.4).D Ø 40.8B Ø 41.4C Ø 42A Ø 42.5B L2L 45.9A L2L 46D L2L 46.2C L2L 47A Seiko SRPD51Ø 42.5 · L2L 46 · lug 22 · T 13.4B Seiko SSC957Ø 41.4 · L2L 45.9 · lug 21 · T 13vs A: Ø −1.1 L2L −0.1 lug −1 T −0.4C Islander ISL-94Ø 42 · L2L 47 · lug — · T 13vs A: Ø −0.5 L2L +1 T −0.4D Seiko SARX055Ø 40.8 · L2L 46.2 · lug — · T 11vs A: Ø −1.7 L2L +0.2 T −2.4
A Seiko SRPD51 and the 3 nearest in size, on one centre, to scaleDrawing from data, not a photo · mm

Nearest in size

  1. ASeiko SRPD51this watch
  2. BSeiko SSC957W −1.1 · L2L −0.1 · T −0.4 mm
  3. CIslander ISL-94W −0.5 · L2L +1 · T −0.4 mm
  4. DSeiko SARX055W −1.7 · L2L +0.2 · T −2.4 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 (18)Seiko SRPD53, Seiko SRPD55, Seiko SRPD57, Seiko SRPD59, Seiko SRPD61, Seiko SRPD63, Seiko SRPD65, Seiko SRPD71, Seiko SRPD73, Seiko SRPD76, Seiko SRPD77, Seiko SRPD79, Seiko SRPD93, Seiko SRPD95, Seiko SRPE74, Seiko SRPG47, Seiko SRPJ45, Seiko SRPJ47

Same movement: Seiko 4R36

All 48 models on the Seiko 4R36

Seiko SRPD51 questions

How big is the Seiko SRPD51?

The Seiko SRPD51 measures 42.5 mm across, 46 mm lug to lug, 13.4 mm thick, 170 g.

Will the Seiko SRPD51 fit a 6.5-inch wrist?

Balanced: the Seiko SRPD51's 46 mm lug to lug takes 86% of the ~53.3 mm flat top of a 6.5-inch (16.5 cm) wrist. By the same estimate (circumference ÷ 3.1) it sits balanced from about 16.5 cm and overhangs the flat top on wrists under about 14.5 cm.

Does the Seiko SRPD51 need a battery?

No. The Seiko SRPD51 has no cell to replace: a wound mainspring drives its automatic Seiko 4R36.

What movement is in the Seiko SRPD51?

The Seiko SRPD51 runs on the Seiko 4R36, an automatic movement.

What strap size does the Seiko SRPD51 take?

The Seiko SRPD51 measures 22 mm between the lugs, so it takes a 22 mm strap with 22 mm spring bars. 45 other models in our base share that width.

Find the strap length for your wrist and the Seiko SRPD51 in the watch strap size tool.

More Seiko watches

Sources

Documents checked · Report a wrong number

  1. 1Seiko Watch Corporation — SRPD51 product page (us-en), seikowatches.com · html · read
  2. 2Seiko Watch Corporation — Instructions: Seiko Automatic Diver's Watch Cal. 4R15/4R16/4R35/4R36/7S26/7S35/7S36 (English) · pdf · read
  3. 3Seiko Watch Corporation — Instructions: Diver's Watch for Air Diving, Cal. 4R35 / 4R36 (English) · pdf · read
  4. 4Grail Watch — Grail Watch Reference: Seiko Cal. 4R36 · html · read
  5. 5Seiko Watch Corporation — Instructions: Mechanical watch, Cal. 4R35 / 4R36 / 4R37 / 4R38 / 4R71 / 4R72 / 4R39 (English) · pdf · read