Movements
Seiko 4R36 caliber reference
The most common Seiko movement, and the one that fixed the 7S26's two omissions.
By Stephen V. · Updated Jul 24, 2026
The Seiko 4R36 is an automatic movement with day and date, running at 21,600 vph with a 41-hour power reserve and 24 jewels. It hacks and hand-winds, which is what separates it from the older 7S26. Seiko specifies it at -35 to +45 seconds per day.
Published specification
| Specification | Value |
|---|---|
| Type | Automatic, bidirectional winding |
| Beat rate | 21,600 vph (6 beats/sec) |
| Jewels | 24 |
| Power reserve | Approx. 41 hours |
| Stated accuracy | -35 to +45 sec/day |
| Hacking | Yes |
| Hand-winding | Yes |
| Complications | Day and date, both quickset |
What it replaced, and why that matters
The 7S26was Seiko’s entry automatic for decades and had two omissions people noticed: no hand-winding and no hacking. The 4R36 adds both while keeping everything else — same beat rate, same reserve, same day-date layout, roughly the same price bracket.
Hand-winding means you can start a stopped watch from the crown rather than shaking it. Hacking means the seconds hand stops when the crown is pulled, so the watch can be set to the second.
Neither changes how the watch keeps time once running. The 4R36’s stated window (-35/+45) is actually slightly wider than the 7S26’s (-20/+40), which surprises people who assume newer means tighter.
Watches that use it
- Seiko 5 Sports SRPD / 5KX family — SRPD65, SRPD91, SRPD93, SRPD55
- Seiko 5 Sports SRPG family — the smaller 39.4 mm references
- Prospex Turtle — SRPE93, SRPE27, and the King Turtle
- Seiko 5 Sports SRPK and SRPJ references
The same movement appears in $250 watches and in $500 ISO 6425 divers. When two Seikos differ in price and share this caliber, the difference is entirely in the case.
The date-change window
Do not use the quickset date between roughly 9 pm and 3 am. During that window the movement’s date mechanism is partially engaged for the automatic changeover, and forcing the quickset against it risks damaging the date wheel teeth. Advance the hands past midday first — the full sequence is in the setting guide.
The watches on this page
Specifications are transcribed from Seiko’s published documentation. Prices come from Amazon and carry the date they were verified. We have not handled these watches — here is what we did instead.
Price as of Jul 24, 2026. Prices move — Amazon's is the one that counts.
#ad · we may earn a commission from this link to Seiko 5 Sports SRPD65
Seiko 5 Sports SRPD65
SRPD65K1Best for: A first mechanical watch you will not outgrow
The SKX case with a movement that hacks and hand-winds. The default answer under $350, and the one most people should stop looking after.
- Spec completeness for the price
- 8.8
- Movement relative to bracket
- 8.5
- Case proportions
- 8.9
- Strap flexibility
- 9.5
- Availability
- 9.0
What it gets right
- Hacks and hand-winds — the SKX's biggest omission, fixed
- 22 mm lugs put the entire aftermarket strap catalog in play
- Day-date in a genuinely legible layout
- Case shape is the SKX profile people actually want
What it gets wrong
- Hardlex, not sapphire — it will scratch
- 100 m and no screw-down crown, so it is not an ISO 6425 diver despite the looks
- 13.4 mm thick under a shirt cuff
Skip this one if: you want an actual dive watch. The 100 m rating and the absence of a screw-down crown mean this is a dive-styled sports watch, not an ISO 6425 diver. The Turtle is the real one.
| Case diameter | 42.5 mm |
|---|---|
| Lug-to-lug | 46.0 mm |
| Thickness | 13.4 mm |
| Lug width | 22 mm |
| Crystal | Hardlex (hardened mineral) |
| Water resistance | 100 m — splash and swim, not scuba |
| Bezel | Unidirectional, 120-click |
| Lume | LumiBrite |
| Caliber | Seiko 4R36 |
| Type | Automatic, hand-winding and hacking |
| Beat rate | 21,600 vph (6 beats/sec) |
| Jewels | 24 |
| Power reserve | Approx. 41 hours |
| Stated accuracy | -35 to +45 sec/day |
| Complications | Day and date |
Price as of Jul 24, 2026. Prices move — Amazon's is the one that counts.
#ad · we may earn a commission from this link to Seiko Prospex Turtle SRPE93
Seiko Prospex Turtle SRPE93
SRPE93K1Best for: An actual dive watch you can also wear daily
A real 200 m ISO-rated diver with a screw-down crown, in the cushion case that wears far smaller than its 45 mm suggests.
- Spec completeness for the price
- 9.0
- Movement relative to bracket
- 8.5
- Case proportions
- 8.8
- Strap flexibility
- 9.5
- Availability
- 8.6
What it gets right
- Genuine ISO 6425 diver, not a diver-styled sports watch
- 47.7 mm lug-to-lug means it fits wrists that 45 mm suggests it should not
- Screw-down crown at 4 o'clock keeps it off the back of your hand
What it gets wrong
- Hardlex on a watch at this price is the recurring Seiko complaint
- The 45 mm figure scares people off before they try one
- Bracelet is adequate, not good
Skip this one if: you have a wrist under about 6.5 inches. The lug-to-lug is forgiving but the case is still visually wide, and the smaller SRPG references exist for exactly this reason.
| Case diameter | 45.0 mm (cushion case) |
|---|---|
| Lug-to-lug | 47.7 mm |
| Thickness | 13.2 mm |
| Lug width | 22 mm |
| Crystal | Hardlex (hardened mineral) |
| Water resistance | 200 m, ISO 6425 rated for scuba diving |
| Crown | Screw-down, at 4 o'clock |
| Bezel | Unidirectional, 120-click, lumed pip |
| Caliber | Seiko 4R36 |
| Type | Automatic, hand-winding and hacking |
| Beat rate | 21,600 vph (6 beats/sec) |
| Jewels | 24 |
| Power reserve | Approx. 41 hours |
| Stated accuracy | -35 to +45 sec/day |
| Complications | Day and date |
Price as of Jul 24, 2026. Prices move — Amazon's is the one that counts.
#ad · we may earn a commission from this link to Seiko 5 Sports SRPG37
Seiko 5 Sports SRPG37
SRPG37K1Best for: Wrists under about 6.75 inches
The small 5 Sports. A 39.4 mm case and 20 mm lugs — this is the one to buy if the 5KX is too much watch for your wrist.
- Spec completeness for the price
- 8.6
- Movement relative to bracket
- 8.5
- Case proportions
- 9.1
- Strap flexibility
- 9.3
- Availability
- 8.5
What it gets right
- 11.7 mm thick — nearly 2 mm slimmer than the 5KX and it shows under a cuff
- Field-watch dial that stays legible
- 20 mm lugs are the most common aftermarket size
What it gets wrong
- 46 mm lug-to-lug is still long relative to the 39.4 mm case
- Hardlex
- No screw-down crown
Skip this one if: you have a 7.5-inch-plus wrist and want presence. At 39.4 mm this reads modest; the Turtle or the 5KX will suit you better.
| Case diameter | 39.4 mm |
|---|---|
| Lug-to-lug | 46.0 mm |
| Thickness | 11.7 mm |
| Lug width | 20 mm |
| Crystal | Hardlex (hardened mineral) |
| Water resistance | 100 m |
| Caliber | Seiko 4R36 |
| Type | Automatic, hand-winding and hacking |
| Beat rate | 21,600 vph (6 beats/sec) |
| Jewels | 24 |
| Power reserve | Approx. 41 hours |
| Stated accuracy | -35 to +45 sec/day |
| Complications | Day and date |
Questions
How accurate is the Seiko 4R36?
Seiko specifies -35 to +45 seconds per day. That is a production tolerance, not a promise about an individual watch, and regulation by a watchmaker typically tightens it considerably.
What is the difference between the 4R35 and the 4R36?
The day wheel. The 4R36 has day and date; the 4R35 has date only. Beat rate, reserve, jewel count and dimensions are otherwise the same.
Does the 4R36 hack?
Yes — the seconds hand stops when the crown is pulled to the time-setting position, which is the main practical upgrade over the 7S26.
Can you overwind a Seiko 4R36?
No. Like any automatic, the mainspring slips at full tension by design. Twenty to thirty crown turns from stopped is plenty; continuing past that does nothing.
How long does a 4R36 last before it needs a service?
Seiko recommends servicing a mechanical watch roughly every three to five years. In practice these movements often run far longer, and many owners replace rather than service them at this price level.
Sources
- Seiko Watch Corporation — US catalog and specifications
- Seiko 5 Sports collection — official specifications
- Seiko instruction manuals and caliber documentation
- Seiko Instruments — movement division (NH-series manufacturer)
Specifications are transcribed from manufacturer documentation and published standards. Where a manufacturer does not publish a figure, this page says so rather than estimating one.
Read next
- Seiko 4R35 caliber referenceThe date-only sibling, and when it is the better choice.
- Seiko 6R35 caliber referenceThe step up, and what the 70-hour reserve costs.
- Best Seiko watches under $500Most of the picks there run this movement.
- How to set a Seiko automaticIncluding the date-change window this movement has.