Sleep Cycle Calculator
Go to bed at one of these times to complete full 90-minute sleep cycles:
Each cycle is about 90 minutes, plus ~15 minutes to fall asleep — waking up between cycles (rather than mid-cycle) tends to feel less groggy. This is a general guideline, not a personalized measurement of your actual sleep.
Free sleep cycle calculator based on 90-minute sleep cycles — enter a wake-up time to see bedtime options, or a bedtime to see wake-up options, for waking up at the end of a full cycle.
How it works
- Choose whether you're planning around a wake-up time or a bedtime
- Enter that time
- See several options, each ending on a full sleep cycle (plus ~15 minutes to fall asleep)
Frequently asked questions
Why 90 minutes?
A typical sleep cycle — moving through light, deep, and REM sleep — lasts about 90 minutes. Waking up at the end of a cycle rather than in the middle of one (especially deep sleep) tends to feel less groggy.
Is this based on tracking my actual sleep?
No — this is a general guideline using the average 90-minute cycle length, not a personalized measurement. Actual cycle length varies somewhat from person to person and night to night.
From the blog
Update history
- 2026-09-02 Launched: sleep cycle calculator for bedtime and wake-up time, based on 90-minute cycles plus fall-asleep buffer. Entirely client-side.