Sleep Cycle Calculator
Find the best time to sleep or wake based on 90-minute sleep cycles. Free.
How to use
The 90-minute cycle
Most adults complete a full sleep cycle (light → deep → REM) in about 90 minutes. Waking at the end of a cycle feels easier than waking mid-cycle. Aim for 5 cycles (7½ hours) on a normal night or 6 cycles (9 hours) for catch-up sleep. Less than 4 cycles (6 hours) and you'll feel it.
It's an average, not a rule
The 90-minute number is the population average. Individual sleep cycles range from 70 to 110 minutes. Total sleep duration and consistency matter more than precisely hitting a cycle boundary. A 7-hour night that wakes you mid-cycle still beats a 9-hour night of frequent disruptions. The calculator is a starting point, not a prescription.
Most adults complete a full sleep cycle (light → deep → REM) in roughly 90 minutes. Waking at the end of a cycle feels easier than waking mid-cycle. Aim for 5 cycles (7.5 hours) or 6 cycles (9 hours). The 'add 14 minutes' often built into these calculators is the average time to fall asleep, per the NHS.
Sleep cycle timing matters less than total sleep duration and consistency. A 7-hour night that hits the cycle boundary still beats a 9-hour night with frequent disruptions. The 90-minute model is an average — individual cycles vary from 70 to 110 minutes.
Frequently asked questions
How long is a sleep cycle?
About 90 minutes on average, though it varies from person to person. Waking at the end of a cycle often feels easier than being woken mid-cycle.
How many sleep cycles do adults need?
Most adults aim for five to six cycles, roughly seven to nine hours of sleep. Needs vary, so use the result as a guide.
Does the calculator allow for falling asleep?
Allow around 15 minutes to fall asleep when choosing a bedtime. This tool is a guide only and is not medical advice.