Tutorial Reading Your Sleep

Tutorial: Reading Your Sleep

What you'll learn: How to understand the Sleep screen — the hypnogram, stage breakdown, efficiency metrics, and what NOOP's on-device sleep detection can and can't do.

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Step 1: Open the Sleep screen

macOS: Click Sleep in the left sidebar.
Android: Tap Sleep in the bottom navigation menu.

You'll see "Last night, read in two seconds" — a clear snapshot of your most recent sleep, broken into four sections:

1. Stage breakdown (the big chart at the top)
2. Night detail (a grid of performance metrics)
3. Stages vs typical (how your night compares to your average)
4. Asleep duration (a 30-day trend)

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Step 2: Read the hypnogram (the stage chart)

What you're seeing:

The stage breakdown shows a visual timeline of your sleep, broken into four stages:

• Deep (dark blue) — the restorative, slow-wave sleep where recovery happens.
• REM (purple) — the dream stage, where memory consolidation and mood regulation occur.
• Light (light blue) — the lighter stage you cycle through between deep and REM.
• Awake (gray) — periods when you were awake, including micro-awakenings.

The chart itself is a hypnogram — a staircase-like timeline showing how your sleep stages flowed across the night. A typical pattern looks like cycles: light → deep → light → REM → awake → repeat.

Under the chart you'll see:

• Total time in bed and efficiency percentage (asleep ÷ in-bed time).
• A note saying "stages approximate (on-device)" if NOOP computed the stages from your strap data; imported WHOOP nights don't have this label.
• A footer showing each stage as:
  REM 1h 15m · 25% | Deep 1h 10m · 23% | Light 2h 40m · 53% | Awake 15m · 5%

Honest note on the hypnogram: NOOP reconstructs the stage timeline from wrist motion, heart rate, and breathing when you wear the strap to bed. It's an educated guess, not a brain-scan (PSG), and the light-vs-deep boundary is the weakest link — don't treat the exact minute counts as precise. The hypnogram shape is more reliable than exact timings. For imported WHOOP data, NOOP only sees stage totals, so it draws a plausible but artificial timeline (deep early, REM later).

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Step 3: Scan the "Night detail" metrics

Below the stage chart is a grid of seven metric tiles. Each shows:

• A headline number (the value for last night)
• A caption showing how it compares to your typical ("vs typical")
• A sparkline showing the last 30 nights as a tiny trend

What each metric means:

Metric	What it is	"Good" vs "typical"
Sleep Performance	How well you slept relative to your personal need	100% = sleeping as much as you need
Efficiency	Time asleep ÷ time in bed (%)	Higher = fewer awakenings/lying awake
Consistency	How steady your bedtimes are	Higher = going to bed at the same time each night
Hours vs Needed	How much you slept vs. your personal average need	100% = meeting your typical need
Restorative	Share of the night spent in deep + REM (%)	Higher = more of the "work" stages
Respiratory	Your breathing rate during sleep (breaths/min)	No universal "good" — your baseline matters
Sleep Debt	Minutes below your personal sleep need	Smaller number = catching up on sleep

Tip: The sparkline in each tile lets you spot trends — is your efficiency trending down? Did a particular habit shift your debt? Compare weeks with different routines.

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Step 4: Compare last night to your typical in "Stages vs typical"

The Stages vs typical section shows three horizontal bars for Deep, REM, and Light.

How to read it:

• The colored bar = how many minutes you spent in that stage last night
• The thin white marker = your personal average (mean) for that stage
• The caption = last night's total, plus how much above or below your typical ("+ 8m vs typ" or "−12m vs typ")

What it tells you:

• If the colored bar extends past the marker → you got more of that stage than usual (usually good for deep/REM, varies for light).
• If the colored bar ends before the marker → you got less than your average.
• Use this to spot which stage you're missing on a low-recovery night. Short on deep? It might explain a tired day.

Platform note: On Android, you'll see the same bars in the same order (Deep, REM, Light). The layout adapts to portrait/landscape.

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Step 5: Check the 30-day sleep duration trend

At the bottom, Asleep duration shows a line chart of how many hours you slept each night over the past 30 days (or fewer if you don't have 30 nights yet).

What you're reading:

• The y-axis shows hours asleep (not hours in bed — so awake time is excluded).
• The x-axis is time, left to right (old to new).
• Avg / Min / Max / Nights appear below the chart.

Why this matters:

This is the longitudinal view — do you see a downward slope? A plateau? Sharp drops on certain days? Use it to correlate with life events: "I slept less that week after the project deadline" or "My sleep improved since I started the new bedtime routine."

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How On-Device Sleep Detection Works

NOOP computes sleep stages using your strap's sensors. Here's what it does and its limits:

What NOOP measures:

1. Wrist stillness — Gravity data (accelerometer) from your wrist. Stillness → likely sleep.
2. Heart rate — Below your daytime baseline → sleep-compatible.
3. Heart-rate variability (HRV) — Parasympathetic tone, which shifts during different sleep stages.
4. Breathing rate — Respiration sensor data; REM typically has more irregular breathing.
5. Motion fraction — Share of epochs that show movement (wake has higher motion).

How it assigns stages:

• Wake — high motion + activated cardiac (elevated HR), OR no clear sleep signal.
• Deep — stillness + high parasympathetic tone (RMSSD) + low HR + regular breathing.
• REM — stillness + activated cardiac + irregular breathing (high RRV).
• Light — everything else; the default when you're asleep but not in deep or REM.

Its honest limits:

1. Can occasionally over-call sleep — a still, awake period (like meditating or lying quietly) might register as light sleep. Wrist stillness alone isn't foolproof.
2. Light/deep separation is the weakest link — without a brain scan, NOOP can't definitively tell deep from light. It uses heart rate and breathing as proxies, which is a good approximation (~65–73% agreement with sleep-lab recordings) but not perfect.
3. Needs the strap worn all night — if you take it off mid-sleep, NOOP can't see that portion.
4. Approximation, not medical — These stages are computed from published HRV and cardiorespiratory methods, not clinical PSG. They're useful for personal trends, not for diagnosing sleep disorders.

See something unexpected? If you wore your strap but the Sleep screen shows "No nights," head to Troubleshooting. If NOOP shows a night but the stages seem off, remember that wrist stillness can fool the detector — a restless night or extended stillness awake will shift the counts.

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If You See "No nights here yet"

NOOP pulls sleep data from two sources:

1. Imported WHOOP export — If you have a WHOOP CSV export, import it in Data Sources to populate your history. Once imported, all those nights appear here.
2. Live strap data — If you're wearing the strap without the WHOOP app, NOOP stores sleep automatically after the first night.

If neither source has data yet:

• New strap user? Wear it to bed tonight. NOOP will detect the session and show it tomorrow.
• No export imported? Go to Data Sources and import your WHOOP CSV export.
• Still nothing? See Troubleshooting.

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Key Takeaways

• The hypnogram is a visual story — Does it show healthy cycling through stages? That's a sign of restorative sleep.
• The metrics are trends, not absolutes — A 20% swing night-to-night is normal; track the 7-day or 30-day average.
• Efficiency is gold — If your efficiency drops below your typical, you're waking more; investigate why (stress, caffeine, heat, light).
• Deep + REM = the restorative work — If Restorative drops below 40%, you're missing recovery stages.
• Sleep staging is approximate — NOOP's on-device method is solid for trends but not clinical. Don't use it to diagnose sleep disorders; see a sleep specialist for that.

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See Also

• Features — Full breakdown of every screen and metric.
• Troubleshooting — No data showing? Hypnogram looks wrong? Find help here.
• Analytics — Deep dive into how recovery, strain, and sleep scoring works under the hood.
• Getting Started — First time using NOOP? Start here.
• FAQ — Common questions about sleep, pairing, and data ownership.