Sleep Cycle Calculator

Bedtime / wake-time planner using the 90-minute sleep-cycle convention plus 14-minute fall-asleep buffer.

I want to…

Wake at a time Sleep now

When

Wake time

The time you need to be awake.

Using current time as the moment you head to bed.

Time display

12-hour 24-hour

Best bedtime

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Suggested times — longest sleep first

Cycles	Sleep	Bedtime

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How this is calculated

Adult sleep runs in roughly 90-minute cycles. Waking at the end of a cycle (light sleep) feels better than waking mid-cycle (deep sleep). We also add a 14-minute fall-asleep buffer — the average time it takes a healthy adult to drift off.

bedtime  = wake − (14 + cycles × 90 min)
wakeTime = bed  + (14 + cycles × 90 min)

Six cycles (≈ 9 hours in bed, 9 hours asleep) is highlighted as the full-rest target for most adults; five (7 h 30 m of sleep) is the common compromise. Three or four cycles are short-night fallbacks — still better than waking mid-cycle.

Times are wall-clock only. Daylight-saving transitions are not modelled; your morning OS clock will already reflect the shift.

How we choose and check our formulas