F-B100W the F-91W shape learns to count steps, for £55

What is new about the Casio F-B100W?

The F-B100W takes the shape of the F-91W, the stepped resin rectangle Casio has sold for decades, and adds two things the original never had: Bluetooth and a motion sensor. It went on sale in Japan on 7 August 2026 and sold out on Casio's own store within hours, according to Notebookcheck. The UK was the first market outside Japan, with Casio UK putting the black F-B100W-1A and teal F-B100W-3A on sale on 17 August 2026 at an RRP of £55. This first look covers the F-B100W-1AEF: black case, black band and a blue ring around the display, the colours most people picture when they think of the F-91W.

The step counter is the headline. The watch counts up to 999,999 steps, lets you set a daily goal between 1,000 and 50,000, and fills a segmented bar across the top of the display as you get closer. A step reminder nudges you after a long spell without moving. Pair it with Casio's WATCHES app and it also sets its own time, gives you around 300 world time cities, keeps a monthly log of steps and calories, and can make your phone ring if you lose it.

How big is it, and how will it wear?

Casio quotes the case at 41.9 x 38.1 x 8.8 mm, so it is 38.1 mm wide, 41.9 mm from top to bottom and 8.8 mm thick. That is a touch larger than the F-91W, but it is still a small watch by modern standards. It weighs just 26 g, so you will barely notice it, even in bed.

Because the case is short from top to bottom, it should sit neatly on almost any wrist. On a wrist of around 15 cm it will look like a classic Casio. On a wrist over 19 cm it will look deliberately small, which is part of the appeal. The band is Casio's familiar slotted design, now made from bio-based resin.

What movement does it use, and how accurate is it?

It is a quartz digital module running on a single CR2016 coin cell. Casio rates the battery at around two years. That is well short of the F-91W's seven years, but there is no charger and no daily routine. Notebookcheck lists Casio's accuracy figure as plus or minus 15 seconds a month without a phone connection. Once paired, the watch corrects itself from your phone, so drift stops mattering if you sync now and then.

The rest of the feature list is classic Casio: a 1/100-second stopwatch that stores up to 200 records, a countdown timer, five daily alarms, an hourly chime, dual time and a fully automatic calendar to 2099. An LED backlight lights the whole display.

How well is it built?

This is a £55 resin watch, and it is built like one. The case, bezel and band are resin and the display sits under resin glass, which will scuff over time. Casio marks it simply "Water Resist" with no depth rating. On Casio's scale that means it copes with rain, splashes and hand washing, not swimming or showering.

There are some nicer touches than the price suggests. Early video footage covered by Notebookcheck shows four polished metal buttons rather than resin ones, and the watch comes in a textured presentation box rather than a plastic tub. The bezel printing is busier than the F-91W's, with "Step Tracker" across the top and "Bluetooth" above the water resistance marking.

Is it good value against its rivals?

At £55 RRP, the F-B100W sits between Casio's own simpler digitals and the cheapest fitness bands. The Casio W-738H costs £45 RRP and swaps the beeping alarm for a vibrating one, but it has no Bluetooth and no step counter. If you want a tougher connected digital, the G-Shock GBD-300 costs £129 RRP and adds G-Shock shock resistance and a water rating you can swim with.

The F-B100W's pitch is different. It gives you a daily step count and a phone-synced clock in a watch that weighs 26 g and runs for years on one cell. Budget smartwatches count steps too, but they need charging every few days and weigh more.

What is the catch?

There are three. First, water resistance is only "Water Resist", so it is not a swimming watch. Second, the step counter is all it tracks: there is no heart rate sensor, GPS or sleep tracking, so it does not replace a fitness watch. Third, it has been hard to buy. Notebookcheck reported that the black F-B100W-1A sold out in the UK soon after launch, and Japanese retailers were working through back-orders into late September. Check stock before you plan a gift around it.

It is also too new for much long-term owner feedback. Battery life with daily syncing and how well the bio-based band holds up are both still open questions.

“An F-91W that sets its own time and counts your steps, and still never needs a charger.”

What do owners say?

Themes from public owner feedback, paraphrased. We never copy Amazon reviews or ratings.

• Early video footage from a Japanese watch channel suggests the display is easy to read and the metal buttons feel a step up from the F-91W.

  Notebookcheck (on a Japanese YouTube video) (opens in a new tab)

• Japanese enthusiast blogs describe it as one of the most sought-after Casios on sale, with buyers waiting weeks for restocks.

  Notebookcheck (citing Great G-Shock World) (opens in a new tab)