Sleep Calculator

Sleep happens in cycles of roughly 90 minutes. Waking up at the end of a cycle (rather than in the middle of one) is commonly associated with feeling more refreshed. Enter a wake-up time or bedtime to see options based on full cycles.

Sleep Calculator

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Wake-up time

Suggested bedtimes (based on full 90-minute cycles)

Assumes about 15 minutes to fall asleep.

How this is calculated

Bedtime option = Wake-up time - (cycles x 90 minutes) - 15 minutes to fall asleep

Example

Waking at 7:00 AM: going to bed at 9:45 PM allows 6 full cycles (9 hours of sleep), 11:15 PM allows 5 cycles (7.5 hours), and 12:45 AM allows 4 cycles (6 hours).

Step-by-step guide

Choose whether you know your wake-up time or your bedtime.
Enter that time.
Pick from the suggested options, each representing a whole number of 90-minute sleep cycles.

Common mistakes

Treating 90 minutes as an exact, universal cycle length - actual sleep cycle length varies somewhat by individual and even night to night.

Prioritizing cycle timing over total sleep amount - most adults need a minimum total sleep duration regardless of where cycles land.

Frequently asked questions

Why does waking up mid-cycle feel worse?

Waking during deep sleep (which happens mid-cycle) is commonly associated with grogginess, while waking during lighter sleep near the end of a cycle tends to feel easier - though individual experience varies.

Is this a substitute for medical sleep advice?

No - this is a general scheduling tool based on typical cycle length. If you have ongoing sleep difficulties, a doctor or sleep specialist can offer guidance specific to you.

How much total sleep should I aim for?

Needs vary by age and individual, but many health organizations suggest 7-9 hours for most adults. Use the options showing 5-6 cycles (7.5-9 hours) as a starting point.

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