Seiko quartz vs automatic

The same-money pair, side by side

The cleanest way to see the difference is to hold everything else roughly equal. The Essentials SUR311 and the 5 Sports SRPD93 are the quartz and automatic Seikos people most often weigh against each other in the same bracket, and both are rated to 100 m. Here is everything Seiko publishes that differs:

The rate and battery figures for the SUR311 come from Seiko’s product page; the 4R36 figures from Seiko’s 4R35/4R36 instruction manual; the case figures from Seiko USA’s pages for the SUR311 and SRPD93.

Accuracy is not close

Seiko states both rates for a watch worn on the wrist between 5 and 35 °C. At the edge of its tolerance, the 4R36 is allowed to gain 45 seconds a day; over a month, that is more than 22 minutes by our arithmetic. The 6N52 is allowed 15 seconds in the same month. Most 4R36 watches run well inside their window and a quartz watch left in the cold runs outside its, but the scale of the gap does not change: quartz is roughly two orders of magnitude more accurate. That is the reason quartz exists, and Seiko is the company that put it on a wrist — the Quartz Astron of 1969 was the world’s first quartz wristwatch.

If accuracy is the thing you care about, this page’s question has an answer and you can stop here; the most accurate Seikos are ranked on their own page.

Power: a battery, a mainspring, or light

The SUR311 runs on a battery Seiko rates at approximately three years, and a battery change is a small, widely available job. The SRPD93 has no battery at all: its rotor winds the mainspring as you wear it, you can also wind it by the crown, and a full wind lasts approximately 41 hours. That last figure is the one that bites. Take an automatic off on Friday night and it has stopped by Sunday, and you set it before you wear it again. The quartz is simply still running.

Seiko also sells the third answer: solar quartz, which charges from light and needs no routine battery change. The SSC700 on this page runs approximately six months from a full charge and is rated at the same ±15 seconds a month; the mechanism is on the solar caliber reference. The hybrid that tried to split the difference, a quartz watch charged by a rotor, was Kinetic, which Seiko no longer lists.

Size: the quartz is five millimeters thinner

The SUR311 is 8.36 mm thick; the SRPD93 is 13.4 mm. That is the difference between a watch that slides under a shirt cuff and one that catches on it, and it follows from what is inside: the 4R36 carries a rotor and a mainspring barrel, the 6N52 does not. The quartz is also the smaller watch across, at 40.2 mm against 42.5 mm. If fit and thickness are your binding constraints, that settles it before movement preference comes up.

What the automatic gives you that no table can

The case for the automatic is real, and it is not about timekeeping. It is a machine you can watch working: the SRPD93 has a see-through caseback, and its seconds hand moves six times a second at 21,600 vph where a quartz hand steps once. It needs nothing but motion to run. It hacks and hand-winds, so it sets to the second. For many people that is the entire point of owning a watch when a phone keeps better time than either, and it is a better reason to buy mechanical than any accuracy argument, because the accuracy argument points the other way.

The cost of the machine is service. A mechanical movement needs periodic servicing; a battery quartz needs its battery changed. What a Seiko service actually costs, and when it is worth doing, is on Seiko service cost.

“Seiko Prospex: quartz or automatic?”

Prospex sells both, which is where this question usually comes from. The automatic Prospex divers — the Turtle on this page, the Samurai — are ISO 6425 rated and are the ones this site ranks. Seiko’s quartz Prospex divers are solar references, and the ones listed at the US retailer we track have no Seiko US specification page behind them, so we do not rank one; the quartz roundup explains that, and the dive roundup covers the automatic side.

Buy the quartz if

• ·You want the watch to be right when you pick it up, every time.
• ·Thickness matters: 8.36 mm against 13.4 mm.
• ·It will be one of several watches, and will sit unworn for days at a time.
• ·You want sapphire at Seiko 5 money: the SUR311 has it and the SRPD93 does not.

Buy the automatic if

• ·The mechanism is the point, and you would look through the caseback.
• ·You never want to think about a battery.
• ·You want a dive-rated watch at this money: the Turtle is an automatic.
• ·You want a first mechanical watch — the automatic roundup ranks the options.

What we are not claiming

We have not timed either watch. The rates above are Seiko’s stated tolerances, not measurements of any example, and the monthly drift figure for the 4R36 is our arithmetic on Seiko’s number at the edge of its window, not a prediction of how any watch will run.