1. Verdict
  2. Price and rivals
  3. Design and comfort
  4. Health and fitness 
  5. Running and workout analysis
  6. Heart rate accuracy
  7. Sleep and health tracking
  8. Smartwatch features
  9. The app – and bugs
  10. Battery life

Casio G-SHOCK GBD-H2000 review

A great smartwatch for athletes – but it could be so much more
Wareable Casio G-SHOCK GBD-H2000 review photo 9
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Casio G-SHOCK GBD-H2000
By Casio
We enjoyed living with the G-SHOCK, which is a lovely watch, comfortable, with bags of personality. Polar’s tech has solved the accuracy issues we ran up against with the H1000, and this is genuinely an excellent sports watch, even for those that are serious about their training. However, the presentation of data on the watch and the app leaves a lot to be desired – and you need to value the aesthetics to look past big smartwatch/sports watch rivals.

  • Bags of personality
  • Great running and workout features
  • Big on accurate data
  • The companion app is poor
  • Some stats are a bit confusing
  • A few bugs to iron out

Casio is back with its next smartwatch, the G-SHOCK GBD-H2000 – and this time it’s serious.

The legendary Japanese watch brand has partnered with wearable tech stalwart Polar, which has provided a bevy of its biometric algorithms, packed into a smartwatch that’s unapologetically G-SHOCK.

You either love G-SHOCK, or it’s not for you. The brand takes no prisoners, but with the GBD-H2000, it’s aiming to make fewer compromises against the likes of the Apple Watch.

The previous generation GBD-H1000 offered much the same proposition: a G-SHOCK for the smartwatch age. But in our review we found some of the workout data wasn’t up to scratch, and it felt like a half-baked smartwatch, too.

> Best smartwatches from our in-depth reviews

Price and rivals

The Casio G-SHOCK GBD-H2000 costs around the same as an Apple Watch so you really need to be invested in the brand and look. As a smartwatch experience, the Apple Watch Series 8 wins hands down.

If you are looking for a workout companion, the Garmin Forerunner 255 is available for significantly less – and the analysis of data is better, thanks to the better app. So again, it really comes down to meshing the G-SHOCK design with good sports tracking – and that's where the Casio G-SHOCK GBD-H2000 hits the sweet spot.

Design and comfort

WareableCasio G-SHOCK GBD-H2000 review photo 4

It’s big, it’s brash – it’s a G-SHOCK. You’ve probably already made up your mind about the design, even by reading this review. And if you’re here for the G-SHOCK look you won’t be disappointed.

We received plenty of positive comments about the look during our review period – which is always a good sign.

It’s not as stupidly huge as the 65mm Casio G-Shock G-Squad Pro GSW-H1000 from 2021 – which runs Wear OS 2.0. 

The Casio G-SHOCK GBD-H2000 is a more manageable 52mm wide, which is still big, but in the realm of a Garmin Fenix 7X (51mm). It somehow managed to sit normally on our slender male wrist, but it’s still nearly 20mm thick – so it’s a big chunk of watch.

The lightweight build helps. Casio has reduced the bulk to 61g, down from over 100g on the previous generation.

WareableCasio G-SHOCK GBD-H2000 review photo 8

The display is a basic MIP LCD – a basic monochrome screen that requires manual backlighting in darkness to read. It’s a throwback to Casios of old.

G-SHOCK is designed for toughness, and it excels here with 200m water resistance – so it's good for a pool and sea – although there aren't any dive-specific features.

There are five buttons on the Casio, and we did find the GBD-H2000 fiddly to navigate – and the buttons oddly quite unresponsive at times, often requiring multiple presses. 

At Wareable we love to credit great smartwatch design – even if it’s not for everyone. And the design and comfort feel on point here, if G-SHOCK is your cup of tea.

Health and fitness 

WareableCasio G-SHOCK GBD-H2000 review photo 6

Despite the retro, digital watch appearance of the G-SHOCK GBD-H2000, there’s a lot going on under the hood.

It’s laden with sensors, including heart rate, gyroscope, accelerometer, and GPS – and it’s designed to track key health metrics, workouts with a focus on running, and sleep.

And of course, this is the first Powered by Polar smartwatch, and it uses 25 algorithms to track key metrics and provide analysis of your fitness.

It features:

•    Sleep tracking – via Polar Nightly recharge
•    Blood oxygen tracking
•    Heart rate monitoring
•    Breathing exercises
•    Step and activity tracking
•    Running/trail running, walking, cycling, gym, swimming (pool and open water)

Running and workout analysis

WareableCasio G-SHOCK GBD-H2000 review photo 3

We took the G-SHOCK out for a variety of runs between 5K and 15K, and were pleased to report excellent performance, in terms of accuracy and analysis, and a rapid GPS lock.

Generally, GPS distance held up in comparison to the multiband GNSS of the Apple Watch Ultra, although on one run, we did find significant wandering.

But multiple 10K runs were tracked within 20m of accuracy – so we're happy to recommend it.

Heart rate accuracy

WareableHR accuracy

Polar’s algorithms certainly did the job in terms of heart rate accuracy – and the G-SHOCK was accurate against a chest strap on long and short runs.

In the sample data above, you can see that the average heart rate across a 55-minute run was 163 bpm vs. 161 bpm via a Garmin Forerunner 255 with HRM-Pro chest strap. Both also clocked a max HR of 177. 

So there can be no complaints about the data that fuels the more advanced analysis. And it was a significant improvement over the H1000.

Head over to the Casio Watches app, and you can see an analysis of your run. 

It’s a decent overview, with heart rate zones, Running Index (which is VO2 Max by another name), Cardio Load, and the percentage of energy you burned from various food sources, e.g. carbs, protein or fat.

We saw data on:

  • Pace
  • Splits
  • Heart rate zones
  • Cadence
  • Stride length
  • Max/min HR
  • Ascent/descent
  • VO2 Max
  • Cardio Load
  • Energy Used (eg. carbs, protein, fat).

Energy Used is an excellent metric that we’ve only seen on Polar watches to date – and can help you analyze whether the session met your goals, particularly if you were aiming to stay in fat-burning zones. 

The VO2 Max estimate seemed low, compared to Garmin’s estimation with a chest strap. It’s impossible to validate scientifically without a sports lab, but we know our fitness levels from previous VO2 Max tests, and Polar’s estimate seemed off, based on five training runs.

If there’s one criticism of the Polar/Casio integration it’s the impenetrable nature of the data. Even as seasoned wearables hacks, we had to do some research to understand the data.

WareableCasio G-SHOCK GBD-H2000 review photo 2

Take the Cardio Status screen (above), which is designed to analyze the volume and load of your training.

You will see Improving/Maintaining/Detraining status, which should give you a guide on how your training is affecting your fitness.

The strain and tolerance numbers felt a little abstract. If you have to Google what a stat means it’s not a great sign of top usability. Strain is this month’s training load, and tolerance is last month’s. 

If you head over to the app, there’s a little more detail – and a nice message such as “You’ve been training less than usual. If you keep this up for long, detraining will occur.” This puts the numbers in content, bvut we do prefer the widgets on the likes of the Forerunner 255 and Fenix, which do a better job of expressing Training Load in our opinion.

But the Casio G-SHOCK GBD-H2000 is actually a fantastic sports watch for runners and people training in the gym or functional fitness – however, as we will come on to, the ecosystem behind it is lightweight.

There’s no way to upload workouts to Polar Flow, Strava or other third parties, which really feels like a missed opportunity, and a lack of information on fitness trends over the longer term.

Sleep and health tracking

WareableCasio G-SHOCK GBD-H2000 review photo 1

The Casio G-SHOCK H2000 is by no means a health watch – and there’s little in the way of ECG, blood pressure, and stress tracking – all of those types of deep metrics we’re seeing on the likes of Apple, Samsung, and Garmin devices.

But there’s plenty being tracked, mostly around the Nightly Recharge and Nervous System Status features.

Nightly Recharge is Polar’s sleep system – but with an eye on readiness, rather than just reporting the hours spent asleep (which it does, and on the whole accurately).

It records the quality of your ‘sleep charge’ with a rating of your sleep out of 100. It’s simple and easy to use.

Also presented is your ANS Charge (autonomic nervous system), which again we had to Google to understand the meaning of the data.

The ANS Charge relates to how your body reacts in the early stages of sleep. It’s quite complex, relating to your heart rate and breathing, and so is the score. We got bad nights of -4.1 but also good nights of +3. The score is a little hard to comprehend, even for those experienced in wearables, and it doesn’t seem to have a direct correlation to improvement. 

Like the Cardio Status feature, Nightly Recharge is one of the more confusing and opaque sleep systems we’ve used.

WareableCasio G-SHOCK GBD-H2000 review photo 5

Head over to the app and you can see your Nervous System Status, which comprises the following data, which is compared to established baselines:

•    Heart rate during sleep
•    Beat-to-beat interval range
•    Heart rate variability
•    Breathing rate

It feels like the Whoop Health Monitor, apart from being nowhere near as actionable or well-presented – a theme of the Casio app experience overall. 

In terms of accuracy – we were happy with these health metrics during our testing. We used Whoop as a benchmark, and while there were differences in absolute numbers, the trends were spot on. Both reported good recovery and also correlated with middling scores due to overtraining or alcohol (or sometimes both). 

Polar also tells you whether you should hit the training or step off, and we liked the “This is a good day for training. Let’s go!” messages.

But the app feels clunky, and there could be so much more done to bring data to life, and help users action the metrics that have been collected. It could be so much better – and that's frustrating.

Smartwatch features


The G-SHOCK GBD-H2000 has a smattering of smartwatch features – so it can pick up some of the core features of the Apple Watch and Android alternatives.

It can display notifications from a paired smartwatch, which can also be read on the wrist.

However, you can either choose to have all notifications on or off. There’s no fine-tuning, such as having calls only, or letting select apps bother your wrist. As a result, we turned off notifications pretty quickly, as we were overwhelmed by wrist buzzing.

And the almanac feature will also display information such as sunrise/sunset times.

But other than that, it’s a very minimal experience. You don’t get wrist payments, apps or any of the bells and whistles of full-fat smartwatches.

The app – and bugs

WareableThe app

When you’re sent a PDF of the manual to go with a review unit of a smartwatch, it’s never a good start. And within a few minutes of trying to pair the G-SHOCK, we were scrolling to page 8 to find out which of the three Casio apps from the App Store we needed to use.

While the older H1000 used the G-SHOCK app, this version resorts to the Casio Watches app. Confusing to say the least.

We didn’t like:

•    Confusing app and quite basic
•    Two nights of sleep data missed without reason
•    Random future days appearing in the My Page stream
•    Lack of trends and longer-term analysis of data

The Casio Watches home screen is pretty much a giant advert for the Casio range and its marketing comms. The next My Watch tab houses all the settings and isn’t somewhere you’ll go on a regular basis.

It’s the third My Page where the action happens. This is essentially a daily stream of cards, a chronological stream of daily activity, sleep overviews, and workouts.

It doesn’t feel like an established fitness and workout app – and that’s a real shame because the H2000 finally feels like a serious fitness device.

Battery life

WareableCasio G-SHOCK GBD-H2000 review photo 7

The final feather in the Casio cap is the monster battery life.

In our two weeks of testing, we didn’t deplete the entire battery life, with multiple runs, sleep tracking, and all-day wear.

Casio hasn’t offered guidance on battery life other than that it will last “weeks” between charges – although it does estimate around 19 hours of GPS tracking with the heart rate monitor turned on.

From our testing, this seems about correct, and five hours of running barely dented the battery.

We’d estimate battery life to be around 2 weeks with around 7 hours of running, all-day wear and sleep tracking – which is excellent.

TAGGED Smartwatches

How we test

James Stables


James is the co-founder of Wareable, and he has been a technology journalist for 15 years.

He started his career at Future Publishing, James became the features editor of T3 Magazine and T3.com and was a regular contributor to TechRadar – before leaving Future Publishing to found Wareable in 2014.

James has been at the helm of Wareable since 2014 and has become one of the leading experts in wearable technologies globally. He has reviewed, tested, and covered pretty much every wearable on the market, and is passionate about the evolving industry, and wearables helping people achieve healthier and happier lives.

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