Sleep Duration Calculator — How Long You Slept

Most adults need 7 to 9 hours of sleep a night, according to the National Sleep Foundation. Enter the time you went to sleep and the time you woke up to find out how many hours you actually slept and whether that falls within the recommended range.

How the calculation works

The math is simple: it’s the hours between the moment you turned off the light and the moment you woke up. If you went to sleep at 11:00 PM and woke up at 7:00 AM, you slept 8 hours. When your bedtime falls on one day and your wake-up time on the next, the calculator crosses midnight automatically — so it works for people who sleep late at night or work overnight.

Keep in mind this number is time in bed, not necessarily effective sleep time. Almost everyone takes a few minutes to fall asleep and wakes up once or twice during the night. So if you’re aiming for 8 hours of sleep, it’s usually worth setting aside a bit more time lying down.

How many hours of sleep by age

The recommended range changes with age. These are the values from the National Sleep Foundation:

Age group	Recommended sleep per day
Newborn (0 to 3 months)	14 to 17 hours
Infant (4 to 11 months)	12 to 15 hours
Toddler (1 to 2 years)	11 to 14 hours
Preschooler (3 to 5 years)	10 to 13 hours
School-age (6 to 13 years)	9 to 11 hours
Teenager (14 to 17 years)	8 to 10 hours
Young adult (18 to 25 years)	7 to 9 hours
Adult (26 to 64 years)	7 to 9 hours
Older adult (65 years or more)	7 to 8 hours

See the browsable version at ideal sleep hours by age and, for little ones, at ideal sleep hours for babies.

Quality matters as much as quantity

Sleeping the right number of hours doesn’t guarantee restful sleep. Two people can both sleep 8 hours and wake up feeling very different: someone who had continuous, deep sleep is more rested than someone who woke up several times. Signs that quality might be poor, even with enough hours:

• Waking up tired, as if you hadn’t slept at all
• Strong sleepiness during the day
• Loud snoring or reports that you stop breathing while asleep
• Taking a long time to fall asleep or waking up in the early hours and not being able to fall back asleep

If any of these show up often, the problem might not be quantity but quality — worth investigating with the sleep quality calculator and, if there’s snoring, with the sleep apnea risk calculator.

How to plan your sleep schedule

If you know what time you need to wake up, you can work backward and figure out what time to go to bed — ideally closing full sleep cycles of about 90 minutes, which reduces the groggy feeling on waking. Use the bedtime calculator and the wake-up time calculator to find the best times, and the sleep cycle calculator to understand the logic behind the 90 minutes.

This content is for informational purposes and does not replace medical evaluation. Persistent poor sleep, snoring with breathing pauses, or intense daytime sleepiness deserve a consultation.