Plan better sleep.
Plan your nights around the mornings you want
All Sleep Calculators works backward from your wake time through complete sleep cycles, so your alarm lands when your body is closest to waking naturally. Free to use, no account needed.
Your usual alarm time.
Most people take 10 to 20 minutes.
Your bedtime options will appear here after you calculate.
Estimates for planning, not medical advice. Cycle timing varies by person and night.
How it works
Tell us your wake time
Start with the morning you need. The calculator also works in reverse if you already know your bedtime.
We count back in full cycles
Sleep runs in cycles of about 90 minutes. We step backward in complete cycles and subtract the time you need to fall asleep.
Pick the bedtime that fits
You get several options, from a full night down to a shorter one. Choose the one your evening allows.
Every sleep tool in one place
Eight free calculators covering the full night: bedtimes, wake times, naps, shift work, jet lag, and recovery.
- Bedtime CalculatorEnter your wake time and get bedtimes timed to sleep cycles.
- Wake Up Time CalculatorEnter your bedtime and find gentler times to wake.
- Sleep Cycle CalculatorSee how many full cycles fit into the sleep you get.
- Sleep Duration CalculatorCompare time in bed with estimated time actually asleep.
- Sleep Debt CalculatorTotal up a week of short nights into one honest number.
- Nap CalculatorTime naps so you wake up clear headed, not groggy.
- Sleep Needs CalculatorRecommended sleep hours by age, from babies to older adults.
- Shift Work Sleep PlannerFit a realistic sleep window around shifts and commutes.
- Jet Lag CalculatorShift your schedule gradually before you cross time zones.
Why sleep cycles matter more than the clock
Sleep is not one long dimming of the lights. It moves through repeating cycles of light sleep, deep sleep, and dreaming, each lasting around 90 minutes. Waking up at the end of a cycle, when sleep is lightest, often feels noticeably easier than being dragged out of deep sleep by an alarm.
That is the whole idea behind these calculators. Instead of guessing a bedtime, you anchor the part of the night you cannot move, usually the alarm, and work backward in complete cycles. The 90 minute figure is an average used for planning; real cycles run roughly 80 to 120 minutes and shift through the night. Treat the suggestions as a starting point, then adjust to what your own mornings tell you over a week or two.
Common questions
How many sleep cycles do I need each night?
Most adults feel best with 5 to 6 full cycles, which works out to roughly 7.5 to 9 hours in bed including the time it takes to fall asleep. The right number varies from person to person, so notice how you feel across a week rather than chasing one perfect number.
Why do I wake up groggy even after 8 hours?
Groggy mornings often come from waking in the middle of deep sleep rather than from the total hours. An alarm that lands near the end of a cycle tends to feel easier. Keeping a consistent schedule matters too; a shifting bedtime can leave you groggy at any duration.
Will a nap ruin my sleep tonight?
Usually not, if it is short and early. Naps of 20 to 30 minutes before mid-afternoon rarely disturb nighttime sleep. Long or late naps can push bedtime later, so keep them earlier in the day.
How accurate is the 90 minute sleep cycle?
It is an average, not a rule. Individual cycles run about 80 to 120 minutes and change through the night and over a lifetime. Our calculators use 90 minutes as a planning estimate, and the methodology page documents every assumption behind the math.