Video summary

Fitbit Charge 6 : Long-term Scientific Review (2024)

Main summary

Key takeaways

Product Review

Fitbit Charge 6 review — key points from the subtitles

Overall impression

The Fitbit Charge 6 is mainly a strong heart-rate + sleep-stage tracker for the price, but with notably disappointing GPS performance. Many improvements versus the Charge 5 seem to be software-driven rather than major hardware changes.

Main features tested

  • Heart rate tracking Compared to a Polar H10 ECG chest strap across:

    • indoors cycling
    • outdoor running
    • outdoor cycling
    • weightlifting
    • Sleep stage tracking Compared to zMAX EEG headband (deep/light/REM, plus discussion of wake time)

  • GPS tracking Tested by repeating the same routes multiple times to check consistency and accuracy

Heart rate tracking performance (strengths & weaknesses)

1) Indoor cycling

  • Correlation: 0.94 (good, but not “perfect”)
  • Common errors: occasional too-high or too-low readings
  • Notable issue: one “really bad” cycling session with significant noise and incorrect HR, likely responsible for dragging overall correlation down
  • Practical take: otherwise “pretty good,” with minor deviations most of the time.

2) Outdoor running

  • Correlation: 0.87 (lower than cycling)
  • Common errors: more likely too-high HR detections at some moments
  • Hypothesized cause: cadence lock (watch tracks running cadence instead of true HR frequency)
  • Overall: mixed—some runs look spot-on, others are significantly worse, but most are “pretty decent.”
  • Comparison: Apple Watches generally do better; Pixel Watch 2 is reported as better than Charge 6.

3) Outdoor cycling

  • Correlation: 0.93 (very solid)
  • Overall: looks pretty good, with some occasional low HR points but good agreement overall.
  • Comparison: Charge 6 performs about as well as Pixel Watch 2 (strong tier) and is substantially better than Charge 5.

4) Weightlifting

  • Correlation: 0.90 (strong for a difficult activity)
  • Observation: fewer missed high peaks than many competitors; peaks are often detected partially (not always fully)
  • Comparison: among the top performers here, comparable to Pixel Watch 2, and much better than Charge 5
  • Best recommendation for true accuracy: use an ECG chest strap for weightlifting.

Overall HR tracking rating

  • Given score: ~4 to 4.5 / 5 stars

Sleep stage tracking performance (strengths)

Compared to zMAX EEG (13 nights)

  • Deep sleep agreement: ~77%
  • Light sleep agreement: ~74%
  • REM sleep agreement: ~62% (lowest of the three, but still “not bad”)
  • Wake time agreement (less emphasized): ~47% (ignored more in conclusions due to known EEG limitations)

Notable observations

  • Deep sleep and REM generally match reasonably well.
  • On two nights, Charge 6 reportedly detected falling asleep too late, missing the first portion of sleep; waking detection was generally fine otherwise.
  • A second dataset from another reviewer (different normalization approach) reportedly shows similar patterns with:
    • ~71% deep
    • ~75% light
    • ~78% REM
    • ~74% awake

Sleep stage competition comparisons

  • Charge 6 is described as “second tier” / solid, not absolute best.
  • Apple Watches and some premium competitors are higher (subtitle references an Oura Ring / ring-like ecosystem; exact list limited by subtitles).
  • Google/Fitbit devices cluster closely together (Pixel Watch 1/2, Versa 4, Sense 2, Charge 5 all similar).
  • Chinese fitness bands (Mi Band, Huawei band) are described as among the worst for sleep-stage tracking.

Sleep stage rating

  • Given score: 4 / 5 stars

GPS tracking performance (major weakness)

Test method

  • Repeated the same routes multiple times (cycling to/from work)
  • Markers show where GPS acquired a signal
  • Consistency judged by how closely tracks overlap

Results

  • Signal acquisition often late (markers far from the start point)
  • Track consistency very poor (tracks “all over the place,” messy paths, straight lines suggesting signal loss)
  • Watch sometimes turns off GPS tracking temporarily during rides

GPS rating & recommendation

  • Given score: ~1 / 5 stars
  • Verdict: the reviewer wouldn’t rely on the Charge 6 for GPS and “cannot recommend it” for that purpose.

Improvements vs. Fitbit Charge 5

  • Charge 6 is described as substantially improved over Charge 5.
  • Improvements are believed to be mostly software, with possible minor hardware tweaks.
  • Charge 5 is described as consistently worse—especially for HR and GPS—while sleep-stage is not presented as a big differentiator.

Comparisons to other wearables (as stated)

  • Apple Watch: generally better for running HR and often best overall for HR/sleep.
  • Pixel Watch 2: often beats Charge 6 for running HR; similar to Charge 6 for outdoor cycling; close/equivalent for weightlifting in charts.
  • Garmin high-end watches (e.g., “Phoenix 7 Pro / Epix 2 Pro”): placed higher than Charge 6 in some HR comparisons.
  • Whoop 4.0 / Oura Ring / Huawei devices: used for tiering; specifics vary by activity.
  • GPS: Charge 6 is singled out as particularly disappointing.

User experience notes

  • Charge 6 is described as a solid all-around health tracker if you don’t rely on GPS.
  • The reviewer mentions a historical Fitbit reliability concern (devices “break quite often” in their experience), but their two Charge 6 units are currently working.
  • Price noted: around $140 on Amazon (in the reviewer’s context).

Concise verdict / recommendation

  • Buy the Fitbit Charge 6 if: you want a good heart-rate and sleep-stage tracker at a reasonable price and don’t care about GPS.
  • Do not buy it if: you need reliable GPS tracking—the review rates GPS around 1/5, citing late acquisition, signal loss, and inconsistent routes.

Speakers contributing different views

  • Main reviewer (Rob): testing, scoring, and comparisons are attributed to Rob in the subtitles.

Original video