Seiko NH35 vs NH38 vs NH36: Complete Movement Comparison

If you're building or buy Seiko mod watches, understanding these movement differences helps you match the right caliber to your dial layout and aesthetic goals. Let's break down the specs, dimensions, and real-world considerations for each.

Side-by-Side Comparison Table

NH35A: The Date Workhorse

The NH35A is Seiko’s most popular modding movement—and for good reason. Known as one of the best Seiko movements, it delivers reliable automatic performance with a single date complication at 3 o’clock.

Key Specifications

• Caliber: 7S26 successor with hacking and hand-winding
• Date Quickset: Yes (pull crown to first position)
• Date Change Time: Approximately midnight (avoid adjusting between 9 PM - 3 AM)
• Dial Compatibility: Requires dial feet positioned to accommodate 3 o'clock date window

Real-World Performance

The NH35A runs at 21,600 bph, which produces a smooth sweep but not quite as refined as higher-beat movements like the 6R35 (28,800 bph). Out of the box, expect accuracy within Seiko's -20 to +40 seconds per day spec, though many examples run closer to +10-15 seconds with proper regulation.

Power reserve sits at 41 hours when fully wound. That means if you take the watch off Friday night, it'll likely stop by Sunday morning unless you use a watch winder.

Why Choose NH35A?

Pick the NH35A when you want a date function without the bulk of a day-date movement. It's the go-to choice for:

• Submariner-style dive watches
• Explorer and Datejust homages
• Any build where you want quick date reference
• Cases designed specifically for NH35 movements

The NH35A's offset dial feet position means you'll need dials cut for this movement—you can't simply swap an NH38 dial onto an NH35 without proper alignment.

NH38A: The No-Date Purist

The NH38A strips away the date complication entirely, offering a cleaner dial layout and centered dial feet positioning.

Key Specifications

• Caliber: Identical to NH35A minus date mechanism
• Dial Feet Position: Centered (not offset like NH35/NH36)
• Weight: Slightly lighter than NH35A due to removed date wheel

Design Advantages

Without a date window cutting into the dial, the NH38A opens up design possibilities:

• Symmetrical dial layouts
• Uninterrupted text and indices
• Vintage aesthetic without date cyclops
• More flexibility with dial artwork and complications

The centered dial feet position also means NH38-specific dials won't fit NH35 or NH36 movements without modification.

Why Choose NH38A?

The NH38A makes sense when:

• You prefer clean, minimalist dial designs
• You're building a vintage-inspired watch (many classic watches lacked dates)
• The date function isn't important to your daily routine
• You want to save $5-10 on movement cost

Popular applications include field watches, pilot watches, and vintage military-style builds where date windows would compromise the historical aesthetic.

NH36A: The Day-Date Classic

The NH36A adds both day and date complications, delivering the classic "President" or vintage Seiko 5 layout.

Key Specifications

• Caliber: NH35A with added day wheel
• Day Languages: Typically English/Spanish, though variants exist
• Day Display Position: 12 o'clock window
• Date Display Position: 3 o'clock window
• Quickset: Both day and date can be quickset via crown positions

Functional Differences

The NH36A uses the same base architecture as the NH35A but adds a day wheel complication. This means:

• Crown position 1: Quickset day (advance by pulling and rotating counter-clockwise)
• Crown position 2: Quickset date (advance by rotating clockwise)
• Crown position 3: Set time with hacking

The day wheel changes automatically at midnight, synchronized with the date change.

Why Choose NH36A?

The NH36A fits specific build styles:

• Day-date homage watches (Rolex Day-Date, vintage Seiko 5)
• Retro and vintage-inspired designs
• Watches where both day and date information add practical value
• Builds using dials specifically designed for day-date layouts

Keep in mind the NH36A requires dials with both day and date windows properly positioned. You can't use an NH35 dial on an NH36 movement without covering the day complication.

Which Movement Should You Choose?

Your choice comes down to dial design, aesthetic preference, and case compatibility.

Choose NH35A If:

• You want date functionality without the day complication
• Your case and dial are designed for NH35 (3 o'clock date window, offset dial feet)
• You're building a modern dive watch, GMT, or everyday sports watch
• You prefer the most widely available movement with maximum parts compatibility

Choose NH38A If:

• You value clean, symmetrical dial layouts
• You're building a vintage, military, or field watch
• You don't reference the date regularly
• You want the lightest movement option
• Your dial design doesn't accommodate a date window

Choose NH36A If:

• You want both day and date complications
• You're creating a vintage Seiko 5 homage or Day-Date style build
• Your dial has windows at 12 o'clock (day) and 3 o'clock (date)
• You appreciate the classic day-date functionality

Custom Builds and Movement Selection

When building a custom Seiko mod, movement choice impacts your entire component selection. Shops like SKYRIM in Nashua, New Hampshire, offer custom builds using NH35, NH38, or NH36 movements paired with your choice of dial, hands, case, and bezel. This modular approach lets you match movement function to your exact design vision—whether that's a clean no-date field watch on an NH38 or a classic day-date build using the NH36.

Prices for custom NH35-based builds typically run $280-$345 depending on case material, crystal type (sapphire vs mineral), and bezel options. Each watch is hand-assembled and pressure-tested to ensure water resistance.

Practical Considerations

Interchangeability

These movements share the same footprint (27.4mm diameter, 5.32mm height), so they fit the same cases. However:

• Dial compatibility is NOT universal due to different dial feet positions (NH38 centered vs NH35/NH36 offset)
• Hands are fully interchangeable across all three movements
• Stem length and crown position are identical

Availability and Pricing

As of 2025:

• NH35A: Easiest to source, $40-$60 depending on supplier
• NH38A: Slightly less common, $35-$50
• NH36A: Moderate availability, $50-$70 due to added complication

Prices fluctuate based on market demand and whether you're buying single units or bulk quantities.

Reliability and Service

All three movements share the same base caliber, meaning:

• Service procedures are nearly identical
• Parts availability is excellent
• Expected service interval: 3-5 years with normal use
• DIY regulation is possible with the right tools

The NH35A has the largest aftermarket support due to its popularity in modding communities.

FAQ

Final Thoughts

The NH35, NH38, and NH36 represent Seiko's accessible entry into reliable automatic movements. Your choice ultimately comes down to complication preference: date-only (NH35), no-date (NH38), or day-date (NH36).

For modern sports watches and everyday wear, the NH35A's date function offers practical value. For vintage builds and minimalist designs, the NH38A's clean dial compatibility wins out. And for classic day-date aesthetics, the NH36A delivers both complications in Seiko's proven architecture.

All three movements share the same accuracy, power reserve, and serviceability—meaning there's no wrong choice, just the right match for your specific build. Whether you're assembling your first mod or commissioning a custom piece, understanding these movement differences ensures your watch functions exactly as intended.