Sleep Calculator
Find the best bedtime or wake-up time based on 90-minute sleep cycles
Mode
I want to wake up at
Sleep Cycle Science
• Each cycle ≈ 90 minutes (NREM + REM)
• ~15 min average time to fall asleep
• Adults need 7–9 hours (5–6 cycles)
• Waking mid-cycle causes "sleep inertia" — grogginess
• Waking after a full cycle = alert and refreshed
Recommended Times
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The 90-Minute Sleep Cycle
Sleep is organized into repeating cycles, each lasting about 90 minutes. Each cycle moves through light sleep (N1, N2), deep sleep (N3), and REM (Rapid Eye Movement) sleep. Deep sleep is most restorative for physical recovery; REM sleep is critical for memory consolidation and emotional regulation.
The key insight: waking up at the end of a complete cycle rather than in the middle dramatically reduces grogginess. This calculator adds ~15 minutes to account for the time it typically takes to fall asleep after lying down.
lightbulb Sleep Tips for India
1Consistent bedtime matters more than duration
2Avoid screens 45 min before bed (blue light blocks melatonin)
3Afternoon nap before 3pm: 20 min (one sleep stage)
✓ Room temp 18–22°C is optimal for sleep