Sleep Cycle Calculator
Work out good times to sleep or wake based on 90-minute sleep cycles.
Waking between cycles
Sleep runs in cycles of roughly ninety minutes, moving from light sleep into deep sleep and back, and waking at the end of a cycle, in light sleep, tends to feel far easier than being jolted out of deep sleep. This suggests bed or wake times spaced by whole cycles, so you aim to wake at a natural break rather than mid-cycle.
Enter a wake time or bedtime to see cycle-aligned suggestions.
A helpful guide, not a precise clock
This is worth treating as a rough aid rather than an exact science. The ninety-minute figure is an average, and real cycles vary between people and night to night, and it takes time to fall asleep in the first place, which shifts everything. So the suggested times are a sensible target, not a guarantee of waking refreshed. What matters far more for feeling rested is total sleep and consistency — going to bed and waking at similar times.
Questions & answers
How long is a sleep cycle?
Around ninety minutes on average, though it varies between people and night to night, so treat cycle timing as a rough guide.
Does waking between cycles really help?
Waking in light sleep tends to feel easier than being jolted from deep sleep, but total sleep and consistency matter far more for feeling rested.
Is anything uploaded?
No. The calculation happens in your browser.