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Seiko watch · 5 Sports · automatic

Seiko SRPG31

The Seiko SRPG31 measures 39.4 mm across, 48.1 mm lug to lug, and 13.2 mm thick, with 20 mm lugs. It fits wrists from ~17 cm (flat-fit estimate).

Sources checked · How we source numbers
Case
39.4 mm1
Lug to lug
48.1 mm1
Thickness
13.2 mm1
Lug width
20 mm1
Seiko SRPG31: size drawingSeiko SRPG31, round case, top and side view to scale: case diameter 39.4 mm, lug to lug 48.1 mm, lug width 20 mm, thickness 13.2 mm. Bezel, dial and crown size are schematic.lug width 20Ø 39.4lug to lug 48.1TOPthickness 13.2SIDE
Seiko SRPG31, top and side, to scaleDrawing from data, not a photo · mm

Seiko SRPG31 specifications

Case diameter
39.4 mm1
Lug to lug
48.1 mm1
Thickness
13.2 mm1
Lug width
20 mm120 mm watches
Weight
77 g1
Crystal
Curved 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
Line
5 Sports1

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 48.1 mm lug to lug covers 88% 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 SRPG31: wrist fitSeiko SRPG31 on a wrist, top view to scale. lug to lug 48.1 mm. Wrist 170 mm, estimated flat width 54.8 mm (circumference / 3.1). Ratio 0.88: balanced.wrist, flat topwrist flat ≈ 54.8lug to lug 48.1Balanced · 48.1 / 54.8 = 0.88estimate: wrist 170 / 3.1 = 54.8 flatcompactbalancededgeoverhang0.750.891
Seiko SRPG31 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 SRPG31 at 1:1, next to a millimetre ruler.

1:1 · not calibrated: sizes are approximate
Seiko SRPG31: size drawingSeiko SRPG31, round case, top and side view to scale: case diameter 39.4 mm, lug to lug 48.1 mm, lug width 20 mm, thickness 13.2 mm. Bezel, dial and crown size are schematic.lug width 20Ø 39.4lug to lug 48.1TOPthickness 13.2SIDE
Drawing from data, not a photo · mm
01020304050

Seiko SRPG31 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 SRPG31 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 4R36

The Seiko SRPG31 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 SRPG31

The models nearest to the Seiko SRPG31 in case width and lug to lug, drawn over it to scale; below, every model within 1 mm of its 48.1 mm.

Size comparison: Seiko SRPG31, Seiko SSK059, Vostok-Europe VK64-515B568, Vostok-Europe VK64-515E628Top-view outlines to scale on one centre. A Seiko SRPG31: Ø 39.4, L2L 48.1, lug 20, T 13.2. B Seiko SSK059: Ø 39.4, L2L 47.9, lug 20, T 13.6 (vs A: Ø 0 L2L −0.2 lug 0 T +0.4). C Vostok-Europe VK64-515B568: Ø 39, L2L 48, lug 20, T 13.5 (vs A: Ø −0.4 L2L −0.1 lug 0 T +0.3). D Vostok-Europe VK64-515E628: Ø 39, L2L 48, lug 20, T 13.5 (vs A: Ø −0.4 L2L −0.1 lug 0 T +0.3).C Ø 39D Ø 39A Ø 39.4B Ø 39.4B L2L 47.9C L2L 48D L2L 48A L2L 48.1A Seiko SRPG31Ø 39.4 · L2L 48.1 · lug 20 · T 13.2B Seiko SSK059Ø 39.4 · L2L 47.9 · lug 20 · T 13.6vs A: Ø 0 L2L −0.2 lug 0 T +0.4C Vostok-Europe VK64-515B568Ø 39 · L2L 48 · lug 20 · T 13.5vs A: Ø −0.4 L2L −0.1 lug 0 T +0.3D Vostok-Europe VK64-515E628Ø 39 · L2L 48 · lug 20 · T 13.5vs A: Ø −0.4 L2L −0.1 lug 0 T +0.3
A Seiko SRPG31 and the 3 nearest in size, on one centre, to scaleDrawing from data, not a photo · mm

Nearest in size

  1. ASeiko SRPG31this watch
  2. BSeiko SSK059W same · L2L −0.2 · T +0.4 mm
  3. CVostok-Europe VK64-515B568W −0.4 · L2L −0.1 · T +0.3 mm
  4. DVostok-Europe VK64-515E628W −0.4 · L2L −0.1 · T +0.3 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 (10)Seiko SRPG27, Seiko SRPG29, Seiko SRPG33, Seiko SRPG35, Seiko SRPG37, Seiko SRPG39, Seiko SRPG41, Seiko SRPH29, Seiko SRPH31, Seiko SRPH33

Same movement: Seiko 4R36

All 48 models on the Seiko 4R36

Seiko SRPG31 questions

How big is the Seiko SRPG31?

The Seiko SRPG31 measures 39.4 mm across, 48.1 mm lug to lug, 13.2 mm thick, 77 g.

Will the Seiko SRPG31 fit a 7-inch wrist?

Balanced: the Seiko SRPG31's 48.1 mm lug to lug takes 84% 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 SRPG31 need a battery?

No. The Seiko SRPG31 has no cell to replace: a wound mainspring drives its automatic Seiko 4R36.

What movement is in the Seiko SRPG31?

The Seiko SRPG31 runs on the Seiko 4R36, an automatic movement.

What strap size does the Seiko SRPG31 take?

The Seiko SRPG31 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 SRPG31 in the watch strap size tool.

More Seiko watches

Sources

Documents checked · Report a wrong number

  1. 1Seiko Watch Corporation — SRPG31 product page (5 Sports), seikowatches.com us-en · 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