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 — SRPD93, SRPD63, SRPJ37, SRPD55
- Seiko 5 Sports SRPG family — the smaller 39.4 mm references
- Prospex Turtle — SRPE99 and the King Turtle SRPE05, plus the smaller PADI SRPE27
- 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.
One consequence of this caliber is worth following up. The day window the 4R36 adds over the 4R35 is the fastest way to tell two near-identical Seikos apart, and best Seiko day-date watches lists which references show it and which calibers drop it.
That stated window is also the answer to the most common worry about this movement. A 4R36 gaining twenty seconds a day is performing to specification, not failing — why a Seiko runs fast or slow sets the published windows against each other and covers the one cause, magnetization, that is worth checking before you pay anybody.
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.
No buyable offer at the last check (October 23, 2026). We show nothing rather than a stale number.
#ad · we may earn a commission from this link to Seiko 5 Sports SRPD93
Seiko 5 Sports SRPD93
SRPD93Best for: A first mechanical watch you will not outgrow
The 5KX case with a movement that hacks and hand-winds, in blue on a silicone strap. 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
- 8.8
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
- Ships on a silicone strap rather than a bracelet
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 | Blue unidirectional rotating |
| Dial | Blue sunray |
| Strap | Black silicone |
| Case back | See-through |
| 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 |
No buyable offer at the last check (October 23, 2026). We show nothing rather than a stale number.
#ad · we may earn a commission from this link to Seiko Prospex Turtle SRPE99
Seiko Prospex Turtle SRPE99
SRPE99K1Best 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
- PADI co-branding on the dial is not for everyone
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 | 13.4 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 elapsed-timing bezel, PADI red and blue |
| Lume | LumiBrite on hands and markers |
| Bracelet | Steel, three-fold clasp with push-button release |
| 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 October 23, 2026. Prices move — Amazon's is the one that counts.
#ad · we may earn a commission from this link to Seiko 5 Sports Field HDB006
Seiko 5 Sports Field HDB006
HDB006Best for: A field watch with a rotating bezel and a mechanical movement
Seiko's current 5 Sports Field: a 41 mm case with a lumed rotating bezel on the familiar 4R36. The field reference the line had been missing.
- Spec completeness for the price
- 8.6
- Movement relative to bracket
- 8.5
- Case proportions
- 8.4
- Strap flexibility
- 9.3
- Availability
- 8.6
What it gets right
- Rotating bezel with its own LumiBrite, which the older field references did not have
- 20 mm lugs, the most common aftermarket size
- The 4R36 hacks and hand-winds
What it gets wrong
- 41 mm with a 48.5 mm lug-to-lug — bigger than the 39.4 mm field references it follows
- Hardlex, not sapphire
- 13.2 mm thick for a field watch
Skip this one if: you wanted the small field Seiko. This is the 41 mm replacement for that idea, and its 48.5 mm lug-to-lug is a different proposition from the 39.4 mm SRPG references, which Seiko has now sold out of.
| Case diameter | 41.0 mm |
|---|---|
| Lug-to-lug | 48.5 mm |
| Thickness | 13.2 mm |
| Lug width | 20 mm |
| Crystal | Curved Hardlex |
| Water resistance | 100 m (10 bar) |
| Bezel | Rotating, with LumiBrite on the bezel as well as the hands |
| Dial | Glossy black |
| Magnetic resistance | 4,800 A/m |
| Case back | See-through, screw case back |
| Clasp | Three-fold with push-button release |
| 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.
- Seiko 4R36 vs 6R35Same beat rate and jewels; the 70-hour reserve is what changes.