Sleep Calculator
Work out when to sleep or wake so your alarm lands at the end of a sleep cycle
Advanced options
One full sleep cycle. 90 minutes is the usual average.
Added before the first cycle starts. 14 minutes is the common convention.
Both Directions
Pick a wake-up time, a bedtime, or start from right now
Six Cycle Options
Times for one through six cycles, with the healthy range flagged
Adjustable
Change cycle length and how long you take to fall asleep
Frequently asked questions
Why 90 minutes per cycle and 14 minutes to fall asleep?
A full sleep cycle averages around 90 minutes, and 14 minutes is the fall-asleep buffer used by the common online sleep calculators (Calculator.net, sleepyti.me). Both are averages, not rules — open Advanced options to set a cycle between 60 and 120 minutes and a buffer between 0 and 60 minutes, and every result recalculates.
Why are 5 and 6 cycles marked as recommended?
Five cycles is 7.5 hours of sleep and six is 9 hours, which brackets the 7 to 9 hours recommended for adults. Four cycles (6 hours) is marked OK as a short night, and three or fewer is shown greyed out because it falls well below the guideline.
Do the results account for crossing midnight?
Yes. Results are times of day only, so a bedtime of 9:46 PM for a 7:00 AM wake-up is simply the evening before, and a wake time of 6:44 AM for an 11:00 PM bedtime is the next morning. The calculation wraps around the 24-hour clock, so no result is ever out of range.
Why do these times differ from just adding 8 hours?
Eight hours is 5 and a third cycles, so a plain 8-hour alarm tends to fire mid-cycle, which is what makes waking feel groggy. The times here are whole cycles plus the fall-asleep buffer, so the nearest options are 7.5 hours (5 cycles) and 9 hours (6 cycles) rather than exactly 8.