Sleep Calculator
Wake up refreshed by timing your sleep with 90-minute cycles. Pick your mode below.
😴 I want to wake up at…
🛏 I need to sleep at…
⚡ Sleep right now
Wake-up time
You should go to bed at one of these times (+ ~14 min to fall asleep):
🧠 Why 90-minute cycles?
Sleep occurs in cycles of roughly 90 minutes, each containing light sleep, deep sleep, and REM. Waking mid-cycle causes grogginess (sleep inertia). Waking at the end of a cycle feels natural.
💤 NREM 1
Light sleep, ~5 min
Light sleep, ~5 min
💤 NREM 2
Body temp drops, ~20 min
Body temp drops, ~20 min
🔵 NREM 3
Deep sleep, most restorative
Deep sleep, most restorative
🌈 REM
Dreams, memory consolidation
Dreams, memory consolidation
Adults need 5–6 cycles (7.5–9 hours). Teens need 6–7 cycles.