38 METRICS · 10 CATEGORIES · 4 DEVICES
What does your wearable track while you sleep?
Every sleep metric across Oura, Fitbit, Apple Watch and Garmin: what each device records, what's exclusive to one brand, and how it's measured. All of it from official documentation.
Best coverage
no device tracks all
22/38
metrics tracked by Oura Ring, the widest coverage of any device here, and still barely half the list.
Counted from each brand's own documentation
38
Sleep metrics compared
10
Metric categories
4
Devices side by side
29
Verified sources
Sleep Metric Comparison
Tap any metric to see how each device measures it.
Oura
22 metrics
Fitbit
21 metrics
Apple Watch
20 metrics
Garmin
21 metrics
Composite Scores
Duration & Timing
Sleep Stages
Sleep Quality
Heart & Vitals
Temperature
Breathing & Apnea
Naps & Coaching
Monthly Analytics
Stress & Recovery
Metric
Oura
Fitbit
Apple Watch
Garmin
Light / Core Sleep
Oura
Called 'Light Sleep', OSSA 2.0 multi-sensor
Fitbit
Called 'Light Sleep', HR and movement classified
Apple Watch
Called 'Core Sleep', ML model in 30-sec epochs
Garmin
Called 'Light Sleep', HR variability and motion
Deep Sleep (NREM Stage 3)
Oura
OSSA 2.0 multi-sensor classification
Fitbit
Classified by low movement and stable low HR
Apple Watch
Classified by sustained stillness and low stable HR
Garmin
Classified by low stable HR and near-zero movement
REM Sleep
Oura
Classified by irregular HRV and low movement
Fitbit
Classified by elevated HR with minimal movement
Apple Watch
Classified by elevated HR with minimal movement
Garmin
Classified by irregular HR with muscle atonia
Awake Time
Oura
Movement and elevated HR during sleep period
Fitbit
Movement and HR patterns indicating wakefulness
Apple Watch
Motion and HR epochs during sleep window
Garmin
Movement and HR patterns indicating wakefulness
Sleep Score (0–100)
7 contributors, weighting proprietary
Fitbit
50pt duration, 25pt stages, 25pt restoration
Apple Watch
50pt duration, 30pt consistency, 20pt interruptions
Garmin
3 pillars via Firstbeat, weighting proprietary
Readiness Score
Combines HR, HRV, temp, recovery, and activity balance
Fitbit
Not available
Not available
Not available
Training Readiness
Not available
Not available
Not available
Combines sleep, HRV, recovery time, and training load
Body Battery Recharge
Not available
Not available
Not available
HRV-based recovery minus stress and activity drain
Total Sleep Time
Sum of light, deep, REM via HR, motion, and temp
Fitbit
Time asleep via accelerometer and HR
Apple Watch
Sum of core, deep, REM in 30-sec epochs
Garmin
Sum of light, deep, REM via PPG and accelerometer
Time in Bed
Bedtime to final wake including awake periods
Fitbit
Sleep start to final wake including awake time
Apple Watch
Schedule start to wake including awake time
Garmin
Sleep Onset Latency
Time from lying down to first detected sleep
Fitbit
Sleep Onset Time
First sleep epoch via movement and HR changes
Fitbit
Detected by HR drop and movement stopping
Apple Watch
First sustained sleep epoch via ML model
Garmin
Detected by HR and movement transition patterns
Wake-up Time
Final sleep-to-wake transition via HR and motion
Fitbit
Detected by sustained wakefulness in HR and movement
Apple Watch
Final sleep-to-wake transition detected
Garmin
Detected by HR and movement at awakening
Sleep Timing (Circadian Alignment)
Scores how well sleep midpoint aligns to circadian rhythm
Fitbit
Sleep Efficiency
Time asleep divided by time in bed
Fitbit
Restfulness / Restlessness
Called 'Restfulness', wake-ups and tossing events
Fitbit
Called 'Restoration', combines HR and tossing
Apple Watch
Called 'Restlessness', tossing and turning count
Nighttime Awakenings (count)
Count of wake epochs, feeds Interruptions sub-score
Garmin
Disrupted Sleep
Monthly mid-sleep awakening frequency (Premium)
Apple Watch
Interruptions Score
Calculated from number and duration of awake periods
Garmin
Bedtime Consistency Score
Compares sleep onset times across last 13 nights
Garmin
Resting / Sleeping Heart Rate
Lowest nighttime HR via infrared PPG
Fitbit
Continuous overnight HR via green PPG
Apple Watch
Continuous overnight HR via green PPG
Garmin
Continuous overnight HR via green PPG
Heart Rate Variability (HRV)
5-min RMSSD samples via infrared PPG overnight
Fitbit
Beat-to-beat via PPG, tracked per sleep stage
Apple Watch
Pulse wave intervals, single overnight value
Garmin
Overnight avg compared against personal baseline
Blood Oxygen (SpO2)
Red and IR pulse oximetry on finger
Fitbit
Red and IR LEDs on wrist, avg and variation
Apple Watch
Red and IR pulse oximetry on wrist
Garmin
Red and IR LEDs on wrist when Pulse Ox enabled
Respiratory Rate
PPG-derived respiratory sinus arrhythmia
Fitbit
PPG and accelerometer cyclic variations
Apple Watch
Accelerometer micro-movements and PPG modulation
Garmin
HRV-derived respiratory sinus arrhythmia
Skin / Wrist Temperature
Finger NTC thermistor, deviation from baseline
Fitbit
Wrist thermistor, deviation from baseline
Apple Watch
Dual wrist sensors every 5 sec, 5-night baseline
Garmin
Wrist thermistor on select models, deviation shown
Breathing Disturbances Detection
Accelerometer wrist micro-movements, ML-classified
Garmin
Breathing Variations Classification
Pulse Ox-derived, rated Minimal/Few/Occasional/Frequent
Sleep Apnea Notifications (FDA)
30-day evaluation, FDA-cleared, accelerometer-based
Garmin
Snoring & Noise Detection
On-device mic classifies snoring by dBA (Sense/Versa 3)
Apple Watch
Nap Tracking
Auto-detects 15 min to 3 hrs with full stage data
Fitbit
Monthly count and duration via Sleep Profile
Apple Watch
Auto-detects since watchOS 11, no stage data
Garmin
Auto-detects under 3 hrs, no stage classification
Sleep Coach / Personalized Sleep Need
Estimates need from activity, sleep history, and HRV
Sleep Profile (10 Monthly Metrics)
10 metrics monthly compared by age and gender (Premium)
Apple Watch
Sleep Animal Archetype
6 animal types from 10-metric clustering (Premium)
Apple Watch
Sleep Schedule Variability
Std deviation of bed and wake times monthly (Premium)
Apple Watch
Stress Level During Sleep
Sympathetic vs parasympathetic ANS activity via HRV
Recovery Index (HR Stabilization)
Hours of sleep after HR stabilizes at nightly low
Fitbit
HRV Balance (14-day vs 3-month)
14-day avg compared against 3-month avg, recent weighted
Fitbit
HRV Status (Rated Category)
Overnight avg vs baseline, rated Balanced to Poor
Exclusive Sleep Features
Features only one device offers, the biggest differentiators for your purchase decision.
Oura Ring
6 exclusive features
- Sleep Onset Latency Time from lying down to first detected sleep; flags sleep issues
- Sleep Efficiency Percentage of time in bed actually spent asleep
- Circadian Alignment Scores how well your sleep midpoint aligns to your circadian rhythm
- Readiness Score Combines HR, HRV, temp, recovery, and activity balance
- Recovery Index Hours of sleep after HR stabilizes at nightly low
- HRV Balance 14-day avg compared against 3-month avg, recent days weighted more
View on Amazon
Fitbit
5 exclusive features
- Sleep Profile (10 Metrics) 10 metrics analyzed monthly, compared by age and gender (Premium)
- Sleep Animal Archetype 6 animal types assigned from 10-metric clustering (Premium)
- Sleep Schedule Variability Standard deviation of bed and wake times monthly (Premium)
- Snoring & Noise Detection On-device mic classifies snoring by dBA level
- Disrupted Sleep Monthly frequency of significant mid-sleep awakenings (Premium)
View on Amazon
Apple Watch
5 exclusive features
- Sleep Apnea Notifications FDA-authorized, 30-day evaluation, accelerometer-based
- Breathing Disturbances ML-classified wrist micro-movements detect respiratory effort
- Nighttime Awakenings Count of wake epochs, feeds Interruptions sub-score
- Interruptions Score Sub-score based on number and duration of awake periods
- Bedtime Consistency Score Compares sleep onset times across last 13 nights
View on Amazon
Garmin
6 exclusive features
- Training Readiness Combines sleep, HRV, recovery time, and training load
- Body Battery Recharge HRV-based recovery minus stress and activity drain
- Stress Level During Sleep Sympathetic vs parasympathetic ANS activity via HRV
- Sleep Coach Estimates personal sleep need from activity, sleep history, and HRV
- HRV Status Overnight avg vs baseline, rated Balanced to Poor
- Breathing Variations Pulse Ox-derived, rated Minimal/Few/Occasional/Frequent
View on Amazon
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Best Wearable by Sleep Priority
What matters most to you? Here’s what the data says.
Sleep Stage Breakdown
All 4 track Light, Deep, REM, and Awake
Sleep Apnea Screening
Only FDA-authorized sleep apnea notifications
Recovery & Readiness
Readiness Score + Recovery Index + HRV Balance
Athlete / Training Recovery
Training Readiness + Body Battery + Stress during sleep
Long-Term Sleep Trends
10-metric monthly Sleep Profile + Sleep Animals
Snoring Detection
Only device with on-device mic for snoring
Sleep Coaching
Personalized sleep need estimation from HRV and activity
Nap Tracking (with Stages)
Only device providing full stage data for naps
Heart & Vitals Coverage
All track HR, HRV, SpO2, Respiratory Rate, Temp
Circadian Rhythm Awareness
Only device scoring circadian alignment
Want every brand on every metric in one place? Open the wearable accuracy hub
Sources
All data sourced from official manufacturer documentation and peer-reviewed research.
Oura Ring
Oura Support: Sleep Score
support.ouraring.com
Oura Ring
Oura Support: Sleep Contributors
support.ouraring.com
Oura Ring
Oura Support: Readiness Contributors
support.ouraring.com
Oura Ring
Oura Support: Heart Rate Variability
support.ouraring.com
Oura Ring
Oura Support: Nap Detection
support.ouraring.com
Oura Ring
Oura Blog: Sleep Score
ouraring.com
Oura Ring
ScienceDirect: Oura OSSA 2.0 Validation
sciencedirect.com
Fitbit
Google Support: Sleep Score
support.google.com
Fitbit
Google Support: Sleep Stages
support.google.com
Fitbit
Google Support: Sleep Profile
support.google.com
Fitbit
Google Blog: Sleep Profile
blog.google
Fitbit
Fitbit: Sleep Technology
fitbit.com
Fitbit
Android Police: Sleep Score Calculation
androidpolice.com
Fitbit
Tom's Guide: Snore Detection
tomsguide.com
Fitbit
My Healthy Apple: Snoring Features
myhealthyapple.com
Apple Watch
Apple Support: Sleep Score
support.apple.com
Apple Watch
The5kRunner: Sleep Score Calculation
the5krunner.com
Apple Watch
Apple Support: Sleep Tracking
support.apple.com
Apple Watch
Apple: Sleep Apnea Whitepaper (PDF)
apple.com
Apple Watch
Empirical Health: Sleep Apnea
empirical.health
Apple Watch
SimplyMac: Nap Tracking
simplymac.com
Apple Watch
Wareable: Sleep Tracking Guide
wareable.com
Garmin
Garmin Blog: Sleep Tracking & Score
garmin.com
Garmin
Garmin Blog: Sleep Score & Insights
garmin.com
Garmin
Garmin Support: Pulse Ox
support.garmin.com
Garmin
Garmin Support: Body Battery
support.garmin.com
Garmin
Garmin: Sleep Tracking Technology
garmin.com
Garmin
Wareable: Garmin Sleep Guide
wareable.com
Garmin
ComputerCity: Garmin Sleep Score
computercity.com
Show all 29 sources
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Data sourced from official manufacturer documentation. Last updated February 2025.
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