Free Tool
Work backward from your alarm.
Sleep runs in cycles of roughly ninety minutes, and waking mid-cycle is what groggy mornings are made of. Pick a wake-up time to get bedtimes, or a bedtime to get wake-up times — the math runs right here.
Be in bed with the lights out by…
Each time includes about 15 minutes to drift off. Times that cross midnight are already wrapped.
9:45 PM
6 cycles · 9h of sleep · recommended
11:15 PM
5 cycles · 7h 30m of sleep · recommended
12:45 AM
4 cycles · 6h of sleep
2:15 AM
3 cycles · 4h 30m of sleep · a short night
Sleep cycles are an average — yours run shorter or longer and vary night to night, so treat these as starting points and adjust by how you actually feel in the morning.
The 90-minute-cycle idea, honestly
During the night, your sleep descends from light sleep into deep sleep and back up through REM, in loops that average about ninety minutes. Waking at the top of a loop — in light sleep — tends to feel easy; waking from the bottom of one is the alarm-clock ambush. The calculator simply counts backward (or forward) in ninety-minute steps, plus a fifteen-minute allowance for falling asleep.
The honest caveat: cycles are averages, not clockwork. Use the times to find a schedule, then let consistency do the real work — a steady wake-up time is worth more than perfect arithmetic. Our sleep hygiene checklist covers the rest of the setup.
Then let the night take over
Once the timing is set, the falling-asleep part gets easier with a routine: a steady sound started early, two minutes of slow breathing, and a sleep timer that fades everything out after you're under. Our 30-minute wind-down routine sequences exactly that, and how long to play sleep sounds settles the all-night-vs-timer question. If your mind is the problem rather than the schedule, a sleep story gives it somewhere softer to go.
Sleep calculator questions.
More free tools
Breathing Exercise Timer
A guided pacer for box breathing, 4-7-8, and simple resets — one, three, or five minutes.
Sleep Sound Mixer
Layer the app's free nature sounds with per-sound volumes and a fading sleep timer — right in your browser.
Which Sleep Sound Matches You?
Five questions, one sound, no email — find your starting point in the sound library.
Tonight could be your calmest night yet.
Download Calming Galaxy free and turn any evening into a quiet, cosmic wind-down.
