Casio F-91W Review: A Fresh Look at the Best-Selling Watch Of All Time

The Casio F-91W is the best-selling wristwatch of all time, with more than 100 million units sold. This statement comes a pretty significant caveat, which depends on whether or not you consider the Apple Watch — well, a watch. I am a defender of “smartwatches,” but I think they have evolved to the point where “wearable” is a more appropriate term given the fact that their functionality when it comes to communication and health monitoring exceeds what any watch has ever done. So, with that established for the sake of this article, let’s put the 300 million Apple Watch sales aside for now.

Casio F-91W History And "Controversy"

The Casio F-91W was introduced all the way back in 1989 and is still in production, with the astonishing figure of 3 million units per year. What's even more remarkable is the fact that the Casio F-91W you can buy in 2025 basically looks the same as one you could have bought when it first launched 36 years ago. It was also the first watch designed by Ryuusake Morai, the prolific designer behind some of the most iconic Casio G-Shocks seen today.

When a watch has been around as long as this, it can transcend fads and trends, but few can claim immunity/teflon status to an unfortunate PR association like the F-91W when it was used as a timer for explosives. I would absolutely not call it a “controversy,” because that would just be silly, but the always-excellent Watches of Espionage has a fantastic article dedicated to the topic, which you can read here. This is a great article that covers some real fascinating and wild history but there are certainly some desperately hysterical clickbait articles and one particularly obnoxious YouTube video that blow the whole thing out of proportion. TL;DR you’ll be fine if you wear this watch and travel just like you’ll be fine if you choose to drive a Toyota pickup truck.

The Casio brand punches above its weight class when it comes to massively famous or rich people wearing its watches (as I mentioned in the case of Bill Gates and the Duro, here) The Casio F-91W is no different, with U.S. President Barack Obama; Chung Eui-sun, the billionaire executive chairman, CEO, and future heir of Hyundai Motor Group; the late billionaire and philanthropist Chuck Feeney, who made his fortune as the co-founder of the Duty Free Shoppers Group; and Rafael Sebastián Guillén Vicente, aka Subcomandante Insurgente Marcos, who was a leader of the Zapatistas (the Mexican rebel group) and a prolific writer.

Case and Strap:

The case of the F-91W is the same now as it was when it was released, measuring 35.2mm wide and 8.5mm thick, with a 38.2mm lug-to-lug measurement (30 meters of water resistance). Made of resin, it’s lightweight and durable without any frills. Some say the case wears a little small but I think that the compact and lightweight (21g) wearability is a significant part of the reason this watch has been such a mainstay for over three decades now.

Personally, I am pretty hard on the aesthetics of about 99% of digital watches out there, but the modest footprint and subtle “authentically vintage” (it’s literally the same watch that debuted in 1989) design goes far here. The resin feels like plastic because, well, it’s plastic. Still, that doesn’t mean it feels cheap. The buttons on the side of the case feel like they are built to work for a few decades, not a few months, and the additional resin bumpers on the sides of the case both help protect the pushers just a little bit and add some visual ruggedness. Finally, the simple, stainless steel caseback is affixed to the case via four screws.

The F-91W has an 18mm lug width and the matching black resin strap is fairly comfortable and gets the job done. That said, it’s pretty easy to switch it out using a spring bar tool. I’ve seen countless F-91W watches with an aftermarket rubber or NATO strap. Frankly, the watch looks pretty good on a NATO but, obviously, watch one of the many instructional videos out there to make sure you do it properly.

Dial and Functions:

The LCD screen of the Casio F-91W is simple and easy to read in low light or bright conditions. It also helps that each of the three buttons is labeled with an arrow pointing to the corresponding pusher, making it simple enough for a child to figure out. The “Light” button on the upper left of the case activates the admittedly not-so-strong green light from that side of the dial. The illumination here is meager but practical and gets the job done without draining the battery too much. The button on the bottom right allows you to turn off the alarm and switch between 24-hour or AM/PM mode.

The lower left button reading “Mode” allows you to cycle through the different functions with one push for Alarm mode at which point the button on the right side can be pushed to cycle between alarm clock mode (the alarm goes off at the same time every day), time signal mode (the alarm goes off every hour), or both alarm and time signal mode. Pushing the Mode button twice puts the watch in ST or Stopwatch mode precise to 1/100 second and also has split-second measurement and 1st and 2nd place times. Finally, three pushes of the Mode button allows you to set the time and calendar, which is done in a sequence of seconds, hours, minutes, month, date, and day. Also note that this is an annual calendar, which takes February’s 28 days into account.

Finally, holding down the bottom right button for about three seconds will have the screen read “CA510” which is something Casio implemented to ensure that the watch is not a counterfeit. Yes, counterfeiting a $20 watch is big enough of a business that Casio felt the need to add this functionality.

Movement and Battery:

The tried and tested Module 593 quartz movement offers the aforementioned stopwatch/split-seconds, alarm/signal, annual calendar, and backlight functionality and is accurate to +-30 seconds/month. It uses the CR2016 battery, which will last you about seven years and cost about 50 cents a piece. Of course, your mileage will vary, but Casio assumes use of the alarm for 20 seconds/day and backlight 1 second/day to reach the seven year figure.

Casio F-91W Variants:

The original Casio F-91W-1 design seen here has the classic black case with blue ring but there have been a lot of variants produced. There is the F-91W-3 which has a black case with a green ring, the F-91WG-9Q is black with an almost-vintage looking brown ring, the F-91WM-9A is a gold colored case with black strap, the F-91WM-7A has a silver case with black strap, the F-91WM-3A has a forest green case with black strap, the F-91WM-2A  has a bright blue case with black strap, and the F-91WM-1B has a grey case with black strap.

There are also the fun "Jelly" models, which are colorful with matching translucent straps. The F91WS-2 comes in a baby blue, the F91WS-4 is pink, the F91WS-7 is white translucent, and the F91WS-8 is grey. Casio also introduced the F-91WB models, which are sleek and a bit more minimalist due to less text on the dial. These options are the F-91WB-1A which is all black, the F-91WB-2A1, which is all blue, the F-91WB-7A, which is all white, and the F-91WB-8A, which is black with beige accents. Finally, there is the F91WPC-1A PAC-MAN collaboration, which comes with a special presentation box and costs about twice as much as the other models at $60.

Value and Final Thoughts:

The Casio F-91W retails for $22.95 and can be had for as little as $16 when on sale (which it frequently is). It’s hard to imagine a better value out there and that estimated 3 million unit annual production number is a testament to the reputation of the F-91W. In fact, there are some videos out there putting this watch through its paces, and in one of them the watch was tested to a water resistance of 60 meters, which is twice what Casio advertises. Another video had the watch strapped to the tire of a Chevrolet Silverado, which drove over it a couple of times — and while the watch was certainly damaged, it was still running.