Free tool
Sleep Time Calculator
Set your wake-up time and how many 90-minute sleep cycles you want, and we'll work backward to the bedtime that lands you between cycles instead of jolting awake mid-cycle.
What this number can’t tell you
One number, one day. The paid report turns it into a plan — the sections it feeds:
- Day schedules1 min
- Weekly checklists1 min
- Playbooks4 min
How we compute this
Sleep runs in cycles of roughly 90 minutes, moving through lighter and deeper stages. Waking up in the middle of a cycle — during deep sleep — tends to feel groggier than waking between cycles, even at the same total hours slept. This is a widely-used practical heuristic for planning bedtimes, not a precise measurement of your own sleep architecture, which varies night to night.
We work backward from your wake-up time: cycles × 1.5 hours gives total sleep duration, plus 15 minutes to allow for actually falling asleep, to land on a bedtime. The healthy range for adults is generally 7-9 hours a night — 4 cycles (6h) sits below that range, while 5-6 cycles (7.5-9h) covers it.
Questions people ask
Set the wake-up time above to 6:00 am and pick a cycle count — the bedtime updates instantly using the same 90-minutes-per-cycle-plus-15-minutes-to-fall-asleep logic described above, so you can see the exact bedtime for 4, 5 or 6 cycles rather than a single fixed number.