Find the best times to go to bed or wake up, based on 90-minute sleep cycles.
How the sleep calculator works
Waking at the end of a sleep cycle can leave you feeling more refreshed than waking mid-cycle. Tell this calculator when you want to wake up (or that you’re going to bed now) and it suggests times built around 90-minute cycles, plus about 15 minutes to fall asleep.
Most people do best with five or six complete cycles a night.
How to use it
- Choose “wake up at” or “go to bed now”.
- Enter your wake-up time if relevant.
- Pick one of the suggested times.
The maths behind it
cycle ≈ 90 minutes + ~15 minutes to fall asleep
target 5–6 full cycles (7.5–9 hours)
Worked example
On the values this calculator opens with, the best times is Sleep at…. Underneath, 6 cycles comes out at 9:45 PM and 5 cycles at 11:15 PM. Change any field and every figure updates as you type.
Questions people ask about this
Why 90-minute cycles?
A full sleep cycle averages about 90 minutes. Waking at the end of one, rather than in deep sleep, tends to feel easier.
How many cycles do I need?
Most adults feel best with five or six complete cycles, roughly 7.5 to 9 hours of sleep.
Is the timing exact?
No — cycle length varies by person and night. Use the suggestions as a helpful guide, not a rule.