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- Most adults need 7 to 9 hours of sleep a night. Teens need 8 to 10 and school-age children 9 to 12.
- A sleep cycle lasts about 90 minutes, so bedtimes that fit whole cycles can help you wake more easily.
- To wake at 7:00 AM and take 15 minutes to fall asleep, go to bed at 9:45 PM for 9 hours, 11:15 PM for 7.5 hours or 12:45 AM for 6 hours.
- Older adults (65 and over) need about 7 to 8 hours.
How to use the sleep calculator
Enter your age
Type your age in years. For a baby, use a decimal such as 0.5 for six months.
Set your wake-up time
Choose the time you need to get up.
Add the time to fall asleep
In More options, change how many minutes it usually takes you to fall asleep. The default is 15.
Read the results
You see the recommended hours for your age and bedtimes that fit 6, 5 or 4 full sleep cycles.
How much sleep do I need?
Sleep needs change with age. Babies sleep most of the day, and the need falls steadily through childhood. The ranges below follow general guidance from sleep medicine groups. Hours for babies and children include naps.
Recommended sleep by age
Per 24 hours.
- Newborns (0 to 3 months) 14 to 17 hours
- Infants (4 to 11 months) 12 to 16 hours
- Toddlers (1 to 2 years) 11 to 14 hours
- Preschoolers (3 to 5 years) 10 to 13 hours
- School age (6 to 12 years) 9 to 12 hours
- Teens (13 to 17 years) 8 to 10 hours
- Adults (18 to 64 years) 7 to 9 hours
- Older adults (65 and over) 7 to 8 hours
These are general ranges. Some people need a little more or less.
How the bedtime is worked out
Sleep moves through light, deep and dream stages in cycles of about 90 minutes. Waking at the end of a cycle often feels easier than waking in the middle of one. The calculator counts backwards from your wake-up time.
Bedtime formula
Bedtime = wake-up time − (number of cycles × 90 minutes) − minutes to fall asleep
6 cycles = 9 hours
5 cycles = 7.5 hours
4 cycles = 6 hours
Cycle length varies from person to person, so treat the times as a guide.
Worked examples
Wake at 7:00 AM, 15 minutes to fall asleep
Count back whole cycles.
The 5-cycle option fits many adults.
Wake at 6:30 AM, age 70
Recommended sleep is 7 to 8 hours.
The 5-cycle option of 7.5 hours is within the 7 to 8 hour range.
Where a sleep calculator helps
Better mornings
Pick a bedtime that matches your alarm.
Parents
Check hours for kids and teens by age.
Shift changes
Plan sleep before an early start.
Catch-up
Check how many hours you owe with the sleep debt calculator.
Talk to a doctor if you sleep the recommended hours but still feel exhausted, snore loudly, stop breathing during sleep, or often cannot fall or stay asleep. This calculator is general guidance and not medical advice.
Sleep calculator FAQ
How much sleep do I need?
Most adults need 7 to 9 hours a night. Teens need 8 to 10, school-age children 9 to 12, and adults over 65 about 7 to 8.
How many sleep cycles do I need?
Many adults do well with 5 or 6 cycles, which is 7.5 or 9 hours.
How long is a sleep cycle?
About 90 minutes on average, though it can be a little shorter or longer.
Is 6 hours of sleep enough?
Most adults need at least 7 hours. Some people feel fine on less for a while, but regular short sleep is linked with health problems.
How much sleep do teenagers need?
8 to 10 hours a night is the general guidance for ages 13 to 17.
How much sleep do babies need?
Newborns sleep 14 to 17 hours and infants 12 to 16 hours a day, including naps.