Casio F-91W specs

The classic Casio F-91W-1 is remarkably small and light:

Spec F-91W

Case dimensions 38.2 × 35.2 × 8.5 mm

Weight 21 g

Case/bezel Resin

Crystal Resin

Band Resin/urethane

Wrist fit 145–200 mm

Water resistance Water resistant

Battery CR2016

Battery life ~7 years

Accuracy ±30 sec/month

Module 593

Display Digital LCD

Time format 12/24-hour

Stopwatch 1/100 sec, up to 59:59.99

Alarm Daily alarm + hourly signal

Light LED

Calendar Auto-calendar, February fixed at 28 days

Casio officially specifies the dimensions as 38.2 × 35.2 × 8.5 mm and 21 g, with a 7-year CR2016 battery and ±30 seconds/month accuracy.

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A couple of interesting details

It's extremely thin: only 8.5 mm, which is one reason it wears so comfortably.

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It's tiny compared with modern watches. The 35.2 mm width is measured across the case, but the actual visual footprint is even smaller because of the narrow bezel/lugs.

The stopwatch really does display 1/100-second resolution, but it's not intended to be a precision laboratory timer.

The water resistance is basic, intended for things like rain and washing your hands—not swimming/diving. Casio specifically describes it as suitable for everyday water exposure.

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Casio still lists the F-91W as a current/bestselling model, so unlike the A1100B situation we were discussing, this one is very much alive.

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If you're comparing it with the A1100B, I can also give you a side-by-side F-91W vs A1100B comparison, including dimensions, thickness, weight, module/features, and how they actually wear on the wrist.

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