Sleep Calculator
Say when you need to wake up and get the bedtimes that fit whole 90 minute cycles, or enter when you go to bed and get the wake times. Time to fall asleep is included.
Based on an average cycle of 90 minutes, which varies between people. Not medical advice. If you often feel very tired or sleep badly, speak to a GP.
Worked examples
Waking at 7:00
Wake at 07:00, 15 minutes to fall asleep
To wake at: 07:00 Time allowed to fall asleep: 15 minutes Suggested bedtime (5 cycles, 7.5 hours): 23:15 Cycles | Sleep | Go to bed at 6 cycles | 9 hours | 21:45 5 cycles | 7.5 hours | 23:15 4 cycles | 6 hours | 00:45 3 cycles | 4.5 hours | 02:15
Five cycles means being in bed by 23:15.
Going to bed at 23:00
Bed at 23:00, 15 minutes to fall asleep
If you go to bed at: 23:00 Time allowed to fall asleep: 15 minutes Suggested wake time (5 cycles, 7.5 hours): 06:45 Cycles | Sleep | Wake up at 6 cycles | 9 hours | 08:15 5 cycles | 7.5 hours | 06:45 4 cycles | 6 hours | 05:15 3 cycles | 4.5 hours | 03:45
Five cycles gives a wake time of 06:45.
About Sleep Calculator
This sleep calculator finds bedtimes and wake times based on 90 minute sleep cycles. Tell it when you need to wake up and it counts back to the times you should go to bed, or enter the time you get into bed and it counts forward to the times to wake. The time you take to fall asleep is included.
Sleep moves through cycles of lighter and deeper sleep that average about 90 minutes, and many people feel more alert if they wake at the end of a cycle. The NHS says most adults need about 7 to 9 hours of sleep, so five or six cycles are the usual aim. These are averages and not medical advice.
How to use Sleep Calculator
- Choose whether you know your wake time or your bedtime.
- Enter the time and how many minutes you usually take to fall asleep.
- Read the times for six, five, four and three cycles.
Common uses
- Choosing a bedtime for an early start
- Planning a nap or a short night
- Working out when to set an alarm
- Adjusting a routine for shift work or travel
Frequently asked questions
How long is a sleep cycle?
About 90 minutes on average, though it varies between people and from night to night. The tool uses 90 minutes as a simple approximation.
How many hours of sleep do I need?
The NHS says most adults need about 7 to 9 hours. Five cycles give 7.5 hours and six give 9 hours.
Why add time to fall asleep?
Cycles start once you are asleep, not when you get into bed, so the time you take to drop off moves the times later.
Is this medical advice?
No. If you often feel very tired or sleep badly, speak to a GP.