Whoop 4.0 Superknit Band review
Tested November 2023
Whoop has a different approach to fitness trackers compared to most other brands – it sacrifices a display for a minimalist, fashion-conscious approach that relies on a smartphone for accessing tracked data.
There’s a focus on health tracking as you’d expect, and it’s durable, with an IP68 rating (dustproof and water-resistant up to 10-metres deep for 2 hours). The manufacturer claims it can be used for swimming in chlorinated water or saltwater (but not for diving), and it can survive showers, baths and activities such as washing the dishes.
However, it has surprisingly limited tracking for workouts. So is Whoop ushering in the future of wearables, or does it ultimately fall short? We put it through our test labs to find out.
Our guide to the best fitness trackers for 2025 reveals the models that impressed in our labs.
How comfortable is the Whoop 4.0 to wear?
The WHOOP is light and slim and the wristband is soft and comfortable to wear. You can wear it on your upper arm instead of your wrist if you prefer, allowing you to wear a regular watch at the same time.
It weighs 27 grams, which is about the same as a thin fitness tracker, and it measures 25.1 x 36 x 10.3mm (w x h x d). The plastic feels sturdy and well-finished. All in all, full marks for comfort.
Setting up the Whoop 4.0
The process of setting up the app and device is simple enough and you build a profile to track your sleep and fitness.
There are four tabs on the Home screen: overview, sleep, recovery and strain. You can only start workouts using the smartphone app rather than on the device itself, which displays detailed and very technical data, but it’s not always the most useful, focusing more on the strain and recovery parts instead of fully tracking workouts.
There’s a lot of help in the app itself to understand the advanced metrics and scores, but it can look quite busy with lots of figures rather than graphs. Plus, it’s fairly limited in terms of customisations. The app does have coaching you can use for fitness and sleeping.
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What activities can the Whoop 4.0 track?
The Whoop 4.0 includes pulse oximetry (recording your blood oxygen levels), and can track heart rate, sleep and skin temperature. It records your blood oxygen levels constantly, including when you’re sleeping, and tells you calories burned when exercising.
However, it’s pretty limited in terms of workouts – which is surprising considering it’s presented on the app as if it's for committed athletes. If you forget to tell it that you’re doing a workout, you can tell it afterwards and it can recover the heart rate data from the workout.
It also doesn’t have built-in GPS, but you can track distance within the app.
How accurate is the Whoop 4.0?
The accuracy of the heart rate monitor is good overall, but it can be variable. It was very accurate when we tested it when using an exercise bike but the accuracy dropped off during walking.
Blood oxygen is also pretty accurate during exercise, but again the precision can decrease when you’re walking. We gave it four stars overall for health tracking.
Whoop 4.0 battery life
Unfortunately the battery isn’t great. It claims to last five days, which is below average across wearable tech, and we were expecting better especially given there’s no on-device display. It scored just two stars out of five in our tests.
An external battery is used at the charging adaptor, which holds the watch in place allowing it to be used while charging. It takes 2 hours 28 minutes to charge during our tests, which is also pretty slow compared to other wearable tech.
How much is the Whoop Band 4.0?
The Whoop Band is priced a bit differently to other wearables, since you'll be paying through a subscription package that includes the device.
The Whoop Band 4.0 is currently available with a 1 month free trial, after which you'll automatically join its 12-month plan at a cost of £229, which can also be paid monthly. If you don't want to keep the device, you can return it for a one-time cost of £8 if you're within this trial period. After that, you're tied into the 12-month commitment, and once membership has ended, the device will no longer collect, upload, or analyze your biometric data.
Find out more at the Whoop website.
Should you buy a Whoop Band 4.0?
Unless you particularly like the concept and design, we think it's a hard sell. It has more limited functionality than many other fitness trackers, battery life is surprisingly poor considering there’s not much to power, and it’s pricey when you consider the ongoing app subscription costs.
Simple fitness trackers have more abilities and are likely to be cheaper overall. See our full list of fitness tracker reviews for Best Buys that start from under £50.
