Sleep Cycle Calculator

Find the best times to go to bed or wake up based on 90-minute sleep cycles.

Sleep Calculator
Average is 10–20 minutes.
About Sleep Cycles
The four stages of sleep
  1. N1 – Light sleep: Drifting off, easy to wake. ~5 min.
  2. N2 – Light sleep: Heart rate slows, body temperature drops. ~25 min.
  3. N3 – Deep sleep: Slow-wave sleep, hardest to wake. Crucial for physical recovery.
  4. REM: Rapid eye movement, vivid dreams, memory consolidation.

Each full cycle takes roughly 90 minutes. Early-night cycles have more deep sleep; later cycles have more REM. Waking at the end of REM (the end of a cycle) feels lightest.

Tips for better sleep
  • Keep a consistent bedtime and wake time, even at weekends
  • Avoid screens for 30–60 minutes before bed
  • Keep the bedroom cool (16–18°C) and dark
  • Avoid caffeine after 2pm and large meals near bedtime
  • Get morning sunlight to anchor your circadian rhythm
Cycles vs Hours
CyclesSleep durationQuality
34h 30mPoor
46h 00mLow
57h 30mGood
69h 00mOptimal
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Frequently Asked Questions

On average a full sleep cycle lasts about 90 minutes and consists of light sleep, deep sleep and REM sleep. Adults typically need 5–6 complete cycles per night (about 7.5–9 hours).

If your alarm goes off during deep (slow-wave) sleep you'll feel groggy – this is sleep inertia. Waking at the end of a cycle, in lighter sleep, feels much more refreshing. The calculator targets these natural break points.

On average, healthy adults take 10–20 minutes to fall asleep. This calculator adds a default 15 minutes of "sleep latency" to your bedtime calculations – you can adjust it.

The NHS recommends 7–9 hours per night for most adults. Teenagers need 8–10 hours, and children even more. Quality matters as much as quantity – consistent bed/wake times help.

For most adults, 6 hours (4 cycles) is the absolute minimum and not sustainable long-term. It's better than waking mid-cycle at 6.5 hours, but aim for 7.5 hours (5 cycles) or 9 hours (6 cycles) most nights.