Sleep Cycle Calculator — Find Your Best Bedtime or Wake-Up Time
Work backward from a wake-up time or forward from bedtime using 90-minute REM cycles to wake up less groggy
Calculates ideal bedtime and wake-up times by counting complete 90-minute REM sleep cycles plus a 15-minute window to fall asleep, so you wake up between cycles instead of mid-cycle.
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How to use
- Choose either your target wake-up time or your bedtime.
- Pick the best option from the recommended cards, usually 5–6 cycles (7.5–9 hours).
FAQ
- Why calculate in 90-minute blocks?
- Sleep runs in roughly 90-minute cycles of light and deep (REM) sleep, and waking up right at the end of a cycle is when your brain feels the least groggy.
- Could the calculated time be off for me personally?
- Yes — actual cycle length varies from person to person (80–120 minutes) and so does how fast you fall asleep, so treat the result as a helpful estimate rather than an exact science.
- Can I use this for naps too?
- Definitely. Set it for 1–2 cycles (around 20 minutes or 90 minutes) so you wake up between cycles instead of in the middle of deep sleep.