NH35 vs NH36
Choosing the Right Seiko Movement for Your Mod
When it comes to modding a Seiko watch, the most popular movements are the NH35 and NH36. Both are reliable, automatic, and widely supported — but they’re not identical.
If you’re planning to build or buy a modded Seiko, understanding the difference between these two movements can help you make a more informed choice.
The Similarities
Both the NH35 and NH36 are part of the Seiko Instruments (SII) NH series. They are designed as no-date or day-date versions of the same base movement, and share the following features:
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Automatic winding with hand-wind and hacking
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24 jewels
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21,600 beats per hour
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Power reserve of approximately 41 hours
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Built-in shock protection
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Reliable and easy to service
They are also nearly identical in size and mounting, which means parts like hands, dials, and cases are often interchangeable between the two.
The Key Difference
The main distinction between NH35 and NH36 is the day wheel.
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NH35 features a date-only complication.
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NH36 includes both day and date.
That’s it — one extra display complication.
The NH36 is effectively the same movement as the NH35, but with an added day function. If you’re using a dial with a double window (day + date), NH36 is required. If your dial is simpler or you prefer a cleaner layout, the NH35 is the more straightforward choice.
Which One Should You Use?
It depends entirely on your build.
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Choose NH35 if:
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You want a cleaner dial with no day complication
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You’re modding a diver or dress-style build
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You want to minimize visual clutter
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Choose NH36 if:
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Your dial has a double window cutout
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You want the extra functionality
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You’re modding a field or tool-style watch
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There is no mechanical advantage to either. Both are equally accurate and reliable when regulated properly.
Watchbrick’s Approach
At Watchbrick, we primarily use NH35 in our builds. The simplicity and focus of a date-only dial allows us to maintain cleaner layouts and more refined symmetry in the designs. That said, for specific builds where a day-date display fits the aesthetic, we use NH36 and regulate it in-house before final assembly.
Final Thought
NH35 and NH36 are two sides of the same coin. The choice between them isn’t about performance — it’s about preference. If you’re building a mod or buying one, look at the dial and think about what kind of functionality and design you value most.
Either way, you’re getting a proven workhorse of a movement — one trusted by independent modders and watch brands alike.