Find your ideal bedtime and wake-up time based on 90-minute sleep cycles. Wake up refreshed, not groggy. Backed by AASM and Sleep Foundation guidance.
Good sleep isn't just about how many hours you get — it's about waking at the right point in your sleep cycle. Our sleep calculators use the science of 90-minute cycles to help you time your sleep so you wake up feeling rested, alert, and ready for the day. Free, instant, and private.
Have you ever slept 8 full hours and still woken up exhausted? That's because your alarm interrupted you mid-cycle, during deep sleep. A sleep calculator solves this by timing your sleep around complete 90-minute cycles, so you wake during light sleep — when getting up feels natural and easy.
Whether you have a fixed alarm time and need to know when to go to bed, or you're heading to bed now and want to set the smartest alarm, our calculator gives you cycle-aligned times in seconds. It even accounts for the time it takes you to fall asleep.
| Cycles | Sleep Duration | Best For |
|---|---|---|
| 6 cycles | 9 hours | Teens, recovery, catching up |
| 5 cycles | 7.5 hours | Most adults (ideal) |
| 4 cycles | 6 hours | Minimum for a short night |
| 3 cycles | 4.5 hours | Emergency only — not sustainable |
For personalized times, use our Sleep Calculator.
Yes, completely free with no signup. All calculations run in your browser and no data is stored or transmitted.
90 minutes is a population average; real cycles range from 70 to 120 minutes and vary through the night. The calculator improves your odds of waking during light sleep but can't guarantee a perfect wake. Total sleep duration and consistency matter most.
Yes. The calculator works for any sleep schedule, including daytime sleep for night-shift workers. Just enter your planned sleep or wake time. For chronic shift-work sleep issues, consider consulting a sleep specialist.
Consistency. Going to bed and waking at roughly the same times every day, weekends included, does more for how you feel than optimising any single night. Cycle timing helps at the margin; an irregular schedule undermines sleep faster than an occasional late night.
Find your ideal bedtime or wake-up time in seconds. Free, instant, and private.
Open Sleep Calculator →Sleep proceeds in cycles of roughly ninety minutes, each moving through lighter and deeper stages before returning toward wakefulness. Waking near the end of a cycle generally feels easier than waking from deep sleep, which is the principle behind timing a wake-up to a cycle boundary.
The ninety-minute figure is an average rather than a constant. Individual cycles range from about eighty to a hundred and ten minutes and vary through the night and between people. A sleep calculator gives you sensible target times, not a precise schedule.
| Age Group | Recommended Sleep | Approximate Cycles |
|---|---|---|
| Teenagers (14-17) | 8 to 10 hours | 5 to 7 |
| Adults (18-64) | 7 to 9 hours | 5 to 6 |
| Older adults (65+) | 7 to 8 hours | 5 |
| School age (6-13) | 9 to 11 hours | 6 to 7 |
Going to bed and waking at roughly the same times every day, including weekends, does more for sleep quality than optimising any single night. The body's circadian rhythm responds to regularity, and irregular schedules undermine it faster than an occasional late night.