WHOOP 4.0 Fitness Tracker

Membership and what it costs

WHOOP does not sell the 4.0 as a hardware-only purchase. The hardware comes with a membership, and the app and your data sit behind it. Tech Advisor puts it plainly: without the subscription “you can’t access your data so it’s essentially a paywall.” There is no monthly rolling option either; subscriptions carry a minimum commitment, and per Tech Advisor, if you cancel you must keep paying to the end of the minimum period.

The tier that still includes WHOOP 4.0 with a 5-day battery is listed at $149 a year against a $199 compare-at, and the tiers above it ship 5.0 hardware. A second WHOOP page shows $199, $239 and $359. Confirm which hardware ships before you subscribe.

Prices have moved a long way. At launch WHOOP advertised “as low as $18 per month” for new healthcare, government, business and athletics customers. Reviewers in 2022 recorded $30 a month with a six-month minimum, $288 a year or $324 for 18 months, $30 a month or $360 a year paid monthly and $288 if paid annually upfront, and from $20 a month on a 24-month membership ($480 upfront). On 2023-02-15 WHOOP cut the 12-month price from $299 to $239 and the 24-month from $480 to $399.

The recurring cost is the point. Digital Trends calculated a two-year total of $599 for WHOOP, or $478 if paid annually upfront, against $408 for two years of Oura, $400 for an Apple Watch Series 8, $240 for a Galaxy Watch 5 and $270 for a Fitbit Luxe. Cancelling is not a clean exit: WHOOP’s Terms of Use state WHOOP “will continue to support your current 4.0 sensor and Membership for a period of time, but reserves the right to end support at its discretion,” and the lifetime warranty lasts only while the membership is active.

Accuracy: sleep versus exercise

WHOOP claims an average 10% accuracy improvement over the 3.0, based on WHOOP Labs work studying over 4,000 individuals, 20,000+ data sets and 50 million heart beats. That is a manufacturer claim, not an independent measurement.

Thirteen adults wore an ECG reference plus multiple wearables across 536 nights. WHOOP 4.0 showed moderate agreement for nocturnal resting heart rate (CCC 0.91, MAPE 3.00%) and HRV (CCC 0.94, MAPE 8.17%), which the authors called acceptable and which came in ahead of the Garmin Fenix 6 and Polar Grit X Pro. The limits matter: 13 people, sleep only, and no exercise heart rate.

Exercise heart rate is where the record splits, and it should not be smoothed into one verdict. WHOOP attributes inflated readings to a loose band letting natural light reach the sensor. T3 reached the opposite conclusion on exercise, calling the 4.0 “considerably more accurate” than the 3.0 while still logging one hard failure in roughly ten tracked activities. Digital Trends, comparing directly against an Apple Watch Series 8, found WHOOP consistently recording lower average and maximum heart rates. Nobody can tell you whether your unit will read high or low during a workout, only that exercise is the known weak spot.

Where the 4.0 earns its keep is overnight. PCMag’s Health Monitor flagged a resting-heart-rate spike to 120 bpm and an SpO2 drop to 88% three to four days before a positive COVID-19 test, and Tech Advisor’s overnight skin-temperature rise correctly flagged the onset of illness.

Battery, charging and the pack

Treat 3 to 5 days as the real range.

There is no port on the sensor, so the slide-on Battery Pack 4.0 is the only way to charge it. A replacement pack costs $49 to $50. WHOOP’s charging table lists 150 minutes, while its community guidance says about two hours for the pack and about 2.5 hours for the sensor from it. The pack is waterproof and charges the sensor while worn, but it adds bulk: Tom’s Guide notes that with the charger attached the tracker is too bulky to fit into WHOOP Body garment pods. The Verge’s reviewer never got more than one charge out of a pack.

The failure modes cluster here. ZDNET’s first unit had a pack that charged the sensor at about 2% per hour and died after a day. Tom’s Guide’s first unit “didn’t charge,” which the reviewer calls an issue a lot of users have experienced. Community threads from 2023 to 2025 document 4.0 sensors that would not power on and packs that died.

Warranty, support and repairs

There is no user-serviceable hardware and no published parts catalogue. The sensor is sealed and the only replaceable items are the band and the battery pack, both sold as shop accessories. The only documented owner workaround is an unofficial teardown, not a supported repair, and modifications are excluded from the warranty.

WHOOP’s current support article describes a lifetime warranty covering a defective sensor (4.0, 5.0, MG), a defective battery pack (4.0, 5.0, MG) and a sensor damaged in a way that affects functionality or accuracy. Section 18 of the Terms of Use says the warranty runs for as long as the membership is active with no outstanding balance, that WHOOP replaces at no additional charge, and that it is non-transferable. Not covered: lost or stolen sensors and packs, cosmetic damage, packs damaged by improper use, unauthorised modifications, and bands and accessories. Lost devices “including chargers or PowerPack(s)” are excluded, which is the most fragile and most loss-prone part.

So the lifetime warranty is real, but it is conditional on continuing to pay, and the same Terms of Use reserve WHOOP’s right to end 4.0 support at its discretion. A legacy document at whoopinternational.com lists one-year handsets, six-month batteries and six-month accessories; it uses handset language and appears to belong to a different product line.

On durability, the longest test located is GearJunkie’s full year with the device, after which the reviewer reported the device and app still giving actionable recovery guidance, rated sleep monitoring “excellent,” and said the sensor never interfered with any activity including rock climbing. Against that, two reviewers’ first units were non-functional out of the box, and there is no capacity-degradation data and no population failure rate.

Is it worth it?

If you track cardio seriously, want continuous recovery data and can live without a screen, the 4.0 at the entry membership is defensible: the nocturnal accuracy data is respectable, the off-wrist wear positions have no direct equivalent, and the sensor and battery pack carry a lifetime warranty while the membership is active. If you want one device that does everything, or you do not want another bill, the answer is no: a $180 Fitbit-class tracker with a screen, GPS and an ECG, a $240 Galaxy Watch, or a Garmin with Body Battery covers much of the same ground for a one-time cost. Do not pay a 5.0-tier price expecting 4.0 hardware without confirming it, because the tiers above the entry level ship 5.0. And weigh WHOOP’s explicit reservation of the right to end 4.0 support, a risk no 2022-era review flagged.

Which model this is

This page covers the WHOOP 4.0 strap, the fourth-generation screenless tracker from WHOOP, announced on 2021-09-08. It ships in colorways including Arctic Gold, Ivy Rhodium, Onyx and Rose Gold, and the 4.0 sensor works only with a 4.0 battery pack. Do not confuse it with the WHOOP 3.0, the WHOOP 5.0 or the MG medical-grade variant. The listing ASIN is B0BWSF6H4Q.

Sources

Manufacturer:

• WHOOP press release: Introducing WHOOP 4.0
• WHOOP CTO on 4.0 design and accuracy
• WHOOP support: sensor battery drains too quickly
• WHOOP support: battery pack and charging overview
• WHOOP support: replacing WHOOP products (warranty)
• WHOOP Terms of Use
• WHOOP membership tiers and lifetime warranty
• WHOOP product feature and membership tiers

Independent reviews:

• Physiological Reports validation study (Dial, 2025)

Owner reports:

• WHOOP 4.0 won’t turn on (r/whoop)
• Received Whoop 4.0 dead (r/whoop)
• Whoop band and charger teardown (r/whoop)
• Charging issue with a 4.0 device (WHOOP Community)