Seiko 5 movements explained: 4R36, NH35 and 7S26

Seiko 5 movements at a glance

Hacking means the seconds hand stops when you pull the crown out to set the time, so you can set the watch to the second. Hand winding means you can wind the mainspring through the crown, which is handy when the watch has stopped.

The 4R36: the current Seiko 5 Sports workhorse

Most current Seiko 5 Sports watches, including the SRPD series, the SRPK series and the SRPG field models, list the 4R36. Seiko Prospex listings for the SRPK01 Turtle describe it as an automatic with manual winding, 24 jewels, day and date, a stop-second function and about 41 hours of power reserve. Seiko publishes an accuracy range of +45 to -35 seconds per day for this caliber, though many examples run well inside it.

The 4R36 is valued for being robust and easy to service. Its day and date both change through the crown, and it shares parts with the rest of the 4R family. For the watches that use it, see the best Seiko 5 Sports watches.

Best Seiko 5 Sports watches →

The 4R35 and 4R34

The 4R35 is the date-only version of the 4R36. Seiko's SRPL11 and SRPJ93 Prospex listings describe it with manual winding, 23 jewels, a stop-second function and about 41 hours of reserve. You find it in Prospex divers and Presage dress watches more than in the Seiko 5 line, which usually shows both day and date.

The 4R34 adds a GMT hand that points to a second time zone on a 24-hour scale. The Seiko 5 Sports GMT SSK001 listing names the 4R34 with 41 hours of reserve and manual winding. Learn how to read it in how to use a GMT watch.

NH35 and NH36: the same design sold to other brands

Seiko Instruments, part of the Seiko group, sells movements to other watch brands under its own codes. The NH35 is its version of the 4R35, and the NH36 its version of the 4R36. They share the same basic design and features, including hacking and hand winding, but may differ in finishing and the markings on the rotor.

That is why you see NH35 in many microbrand and fashion brand automatics. It is a well proven movement and parts are easy to find. If a non-Seiko watch lists an NH35, expect it to behave like the 4R35 in a Seiko.

The 7S26 and why the switch mattered

Older Seiko 5 watches, including many models from before the 5 Sports relaunch in 2019, and the original SKX divers used the 7S26. It is an automatic with day and date and 21 jewels, but it cannot be wound by hand and does not hack. To start a stopped 7S26, you swing or wear the watch until the rotor gets the spring going.

The move to the 4R36 in the current Seiko 5 Sports range added both features, which makes daily use easier. If you are shopping used, check the caliber in the listing or on the caseback reference. Our page on how to wind a Seiko 5 covers both types.

• To tell them apart: try turning the crown in its pushed in position. If it winds the watch, it is likely a 4R or NH caliber.
• Pull the crown to the time setting position. If the seconds hand stops, the watch hacks.
• The model reference on the caseback, looked up on Seiko's site, confirms the caliber.

Frequently asked questions

Which movement does the Seiko 5 use? Current Seiko 5 Sports models use the 4R36 in most day-date models and the 4R34 in GMT models. Older Seiko 5 watches mostly used the 7S26.

Is the Seiko NH35 the same as the 4R35? They share the same design. The NH35 is the version Seiko Instruments sells to other brands, while the 4R35 goes into Seiko branded watches.

Can you hand wind a Seiko 5? Current Seiko 5 Sports models with the 4R36 or 4R34 can be hand wound by turning the crown in its pushed in position. Older 7S26 models cannot.

How accurate is the Seiko 4R36? Seiko's published range is +45 to -35 seconds per day. Individual watches often do better, and a watchmaker can regulate one that runs far off.