Video summary

Pixel Watch 4 - Full Scientific Review (BETTER and BETTER, but...)

Main summary

Key takeaways

Product Review

Product reviewed

Google Pixel Watch 4 (tested in 45 mm and 41 mm sizes) — positioned as a stronger “Apple Watch Ultra contender” for sports + health, with emphasis on heart rate, sleep stages, and GPS.

Key features mentioned

  • Dual-frequency GPS (hardware upgrade over Pixel Watch 3)

    • Intended to reduce interference and improve GPS lock speed and accuracy.

  • Sleep stage tracking algorithm overhaul

    • Predicts sleep stages using distance between heartbeats plus movement during the night.
    • Includes efforts to be more usable for people with insomnia (not personally testable by the reviewer).
    • Expected changes vs older Fitbit/Google sleep staging:
      • slightly more deep sleep on average / shifts in percent distribution.

  • Heart rate sensor changes (mostly physical/layout)

    • “Mostly the same” sensor, but the rear layout changed, potentially affecting signal performance.

  • Gemini features

    • Described as quick and usable on the watch.

  • Design / display

    • Curved display: the display itself is curved (not only curved glass).
    • Style described as divisive.

  • Charging

    • Side charging cradle/click-in design (new compared to earlier versions on the back).

Testing & user experience (practical takeaways)

Sizes: 45 mm vs 41 mm

  • The reviewer tested both and found 41 mm performed slightly better in some cases (notably running HR and GPS clarity in comparisons).
  • Gemini app/experience was not separated by size; described as generally quick.

Battery (Google-reported via “Rob from the future”)

  • 45 mm: ~40 hours
  • 41 mm: ~30 hours

Hardware differences (Google)

  • Google says there are no meaningful sensor hardware differences between 41 mm and 45 mm (aside from size-related fit/comfort and shielding/light leakage effects).

Performance results (key numerical outcomes)

1) Heart rate tracking

Test types: indoor cycling, running, outdoor cycling, weightlifting.

Indoor cycling (chest strap reference)

  • 45 mm: generally strong, with small over-detection at lower HR ranges
    • Correlation: 0.97
  • 41 mm: even closer agreement
    • Correlation: 0.99

Competition note: Both were among the better performers, though Apple Watches and some others beat them slightly.

Running

  • 45 mm: major issue due to cadence lock on one problematic run
    • Correlation: 0.81
    • Behavior: often reported HR around ~158 BPM when reference HR was lower.
  • 41 mm: almost perfect in the test set
    • Correlation: 0.99

Competition note: The 45 mm result was weaker due to that single run; 41 mm competed with the best (including Apple Watches).

Outdoor cycling

  • 45 mm: very good
    • Correlation: 0.97
  • 41 mm: even better
    • Correlation: 0.98

Overall: Strong HR tracking for outdoor riding; minor low-HR artifacts sometimes.

Weightlifting

  • 45 mm: not good
    • Correlation: 0.86
  • 41 mm: similar performance

Explanation: wrist tension during sets makes HR measurement difficult for most watches. Recommendation: use a chest strap.

Important limitation: Pixel Watch cannot connect to an external HR strap via Bluetooth.

  • It can broadcast HR to other devices, but cannot receive HR data from a strap.
  • Reviewer note: among major smartwatch ecosystems, Apple Watch is the only one that supports external HR monitor input.

2) Sleep stage tracking (vs Zeemax EEG headband reference)

  • 8 nights total tested (with examples described as two iterations, summarized as 8 nights overall).

Agreement percentages (Pixel Watch 4)

  • Deep sleep agreement: ~80% (45 mm) and 82% (41 mm)
    • Confusions mostly with light sleep.
  • Light sleep agreement: ~77% (45 mm) and slightly lower for 41 mm
    • Confusion includes other stages (deep/REM/awake), per reviewer implication.
  • REM sleep agreement: ~70% (45 mm) and ~70% (41 mm)
    • Confusions mostly with light sleep.

Overall: “very good,” and similar performance between 41 and 45 mm.

Competitor comparison: described as on par with Apple Watch and Oura/Eight Sleep (reviewer notes Fitbit/Google algorithm consistency across supported devices).

Extra sleep-stage insight

  • Google stated the newer algorithm increases sleep-stage transitions vs the previous generation (more switching between stages).

3) GPS tracking (dual-frequency vs Pixel Watch 3; compared to Apple Ultra & Garmin-class)

Testing methods

  • Cycling: same route 4x to check overlap.
  • Running: same circle multiple times; includes a side with GPS interference (a wall).

Cycling GPS

  • Acquisition: almost instant (good initial lock).
  • Overlap: sometimes close, but with noticeable deviations and some “weird hooks/twists.”
  • Verdict: not bad, but not as clean as top performers.

Running GPS

  • Clear wall effect: more deviation near the obstruction.
  • Compared to Pixel Watch 3: Pixel Watch 4 is definitely better.
  • Compared to Apple Watch Ultra 3: Ultra looks cleaner (Pixel looks noisier). Apple may use more smoothing/post-processing.

Overall GPS conclusion

  • Pixel Watch 4 GPS is improved vs Pixel Watch 3 (dual frequency), but still shows more noise than top brands (Apple Ultra, Garmin, Coros, Suunto).

Pros (unique points called out)

  • Excellent heart rate + sleep staging overall, especially for Android
  • Sleep stage tracking: strong agreement with EEG reference; deep and REM generally well identified
  • Running HR overall is strong for 41 mm, with reliable indoor and outdoor performance
  • Improved GPS lock speed; dual-frequency likely helps interference handling
  • Gemini features feel responsive/quick
  • Curved display is a notable aesthetic/UX improvement
  • Larger size (45 mm) helps style/fit versus earlier generations (reviewer opinion)

Cons / limitations (unique points called out)

  • GPS still noisier than best-in-class, especially vs Apple Watch Ultra 3 and Garmin-class
  • Running HR variability on 45 mm: one cadence lock incident heavily impacted correlation (possible fit/sensor positioning or algorithm tuning)
  • Weightlifting HR tracking is weak due to wrist tension
  • No external HR strap input support (reviewer: Apple Watch supports it; Pixel does not)
  • App quality: reviewer says the Pixel app may still need improvements; Oura/Whoop have better apps (software/experience level)
  • Style may be polarizing/divisive

Comparisons made

Apple Watch

  • Heart rate: Apple Watches generally slightly outperform on indoor cycling correlation.
  • Sleep stage tracking: Pixel Watch 4 is described as on par.
  • GPS: Ultra 3 produces cleaner, smoother signals (likely more smoothing/post-processing).
  • External HR straps: Apple Watch can connect to external monitors; Pixel cannot.

Pixel Watch 3

  • Sleep algorithm already improved on Pixel Watch 3; Pixel Watch 4 sleep results remain strong.
  • GPS is better on Pixel Watch 4.
  • Heart rate: Pixel Watch 4 matches Pixel Watch 3 in running/cycling except the 45 mm cadence-lock incident.

Garmin / Coros / Suunto (and others)

  • GPS: still behind these brands.
  • Sleep staging: not treated equally—Pixel is described as far ahead in sleep-stage performance.

Oura / Whoop / Eight Sleep

  • Sleep stage tracking: comparable to Apple/Oura/Eight Sleep.
  • App experience: Oura/Whoop perceived as having better apps.

Overall verdict / recommendation

Best overall Pixel Watch for Android health tracking: Pixel Watch 4 is a top-tier device for sleep stages and strong heart-rate performance, with 41 mm often edging out 45 mm in HR accuracy tests.

Main remaining weakness: GPS still not best-in-class, and weightlifting + external HR strap limitations reduce suitability for users who rely on those workflows.

Recommendation

  • Get Pixel Watch 4 if you want excellent sleep stage tracking and good-to-very-good wrist HR for everyday training and cycling.
  • If you prioritize precision GPS (especially near obstructions) or weightlifting HR with a chest strap, consider alternatives—while noting Pixel Watch’s HR strap input limitation.

Points by speaker

Only Rob is clearly identified as the main speaker (including “Rob from the future” segments). No other distinct speakers with separate review perspectives were identified in the subtitles.

Original video