NEW

Sleep Cycle Calculator

Best bedtimes & wake times on 90-min cycles.

About this calculator

Sleep runs in roughly 90-minute cycles, and waking up at the end of a cycle feels far better than being dragged out of deep sleep mid-cycle. This calculator works backwards from your alarm to suggest bedtimes that land on complete 6, 5 or 4 cycles.

Alternatively, use "Sleep now" mode when you are heading to bed: it adds 4.5, 6, 7.5 and 9 hours to the current time so you can set an alarm that wakes you between cycles instead of in the middle of one.

How to use

Choose "I wake up at…" or "Sleep now" mode.
In wake mode, set your alarm time.
Pick the bedtime matching 6, 5 or 4 full 90-minute cycles.
Allow about 15 minutes to actually fall asleep after lights out.

Frequently asked questions

Why 90-minute cycles?

Human sleep naturally cycles through light, deep and REM stages in about 90 minutes. Waking at a cycle boundary avoids the grogginess of deep-sleep interruption.

How many cycles do I need?

Most adults feel best on 5–6 cycles (7.5–9 hours). Four cycles (6 hours) works occasionally but is not enough long-term.

Does it count the time to fall asleep?

No — add roughly 15 minutes after getting into bed before the first cycle starts.