Sleep Cycle Calculator
Plan your night around 90-minute sleep cycles. Pick whether you want to wake at a specific time or you're going to bed now.
We'll suggest bedtimes that end on a complete cycle.
Default 15 minutes — the average for healthy adults.
9:45 PM
6 cycles · 9h sleep
11:15 PM
5 cycles · 7.5h sleep
12:45 AM
4 cycles · 6h sleep
Why sleep cycles matter
Sleep moves in repeating 90-minute cycles of light, deep and REM sleep. Waking at the end of a cycle leaves you alert; waking mid-REM leaves you groggy. The buffer you set above accounts for the time it takes to drift off — 15 minutes is the typical average.
What your sleep times mean
The suggested bed and wake times are spaced around 90-minute sleep cycles, plus ~15 minutes to fall asleep. Waking at the end of a cycle — rather than mid-cycle — tends to feel less groggy.
Everyone's cycle length varies slightly (80–110 minutes), so treat the times as guidance. If you consistently wake tired at one time, try the next option earlier or later.
When to use the sleep cycle calculator
It helps most when you have a fixed wake time (an early flight, an exam, a workout) and want to pick the best bedtime, or when you're planning a nap and want to avoid waking mid-cycle.
For everyday sleep, keeping a consistent schedule and getting 7–9 hours matters more than hitting an exact cycle boundary.
Frequently asked questions
Why 90 minutes?+
A full sleep cycle averages about 90 minutes (light → deep → REM). Waking at the end of a cycle leaves you feeling more refreshed than waking mid-REM.
Why the 14-minute buffer?+
Healthy adults take ~10–20 minutes to fall asleep. We add 14 minutes so the cycle math lines up with when you actually drift off.
How many cycles should I get?+
Most adults need 5–6 full cycles per night (7.5–9 hours). Four cycles (~6 hours) works for short stretches but isn't sustainable.
What if I miss the exact time?+
Aim for within 10 minutes of a suggested time. Sleep onset varies day to day — don't stress the clock.
Health disclaimer: Caloritix provides estimate-based health and fitness calculators for general educational purposes only. Results are not medical advice and should not replace guidance from a qualified healthcare professional.