Adolescent Sleep Deficit Calculator

1. Pick the age group and school start. Choose teen (13 to 18) or child (6 to 12), then enter when school starts and how long getting ready and travel take. That sets the latest wake-up time.
2. Enter the usual school-night bedtime. Use the time the lights go out, plus the minutes it usually takes to fall asleep.
3. Add a weekend wake-up time (optional). The calculator compares it with the school-day wake-up time.

An adolescent sleep deficit is the gap between the sleep a young person needs and the sleep a school-night schedule actually allows. The NHLBI, with the American Academy of Pediatrics (AAP) endorsing the ranges, gives 8 to 10 hours a day for ages 13 to 18 and 9 to 12 hours for ages 6 to 12.

The deficit adds up. Losing 2 hours a night is 10 hours over a school week, which is more than a full night of sleep. Most of the loss is set by two things the student cannot easily change: the school start time and the time the trip to school takes. The bedtime is the part that can move, which is why this tool starts from the morning and works backwards.

For the wider picture of what short sleep does to teens, read the teen sleep deprivation guide. For other ages, use the sleep calculator by age.

The calculator counts backwards from the school bell, then compares the sleep your bedtime allows with the bottom of the recommended range.

1. Latest wake-up: 7:30 AM – 60 min = 6:30 AM.
2. Asleep at: 11:00 PM + 30 min = 11:30 PM.
3. Sleep: 11:30 PM to 6:30 AM = 7 h 00 min.
4. Deficit for a teen: 8 h – 7 h = 1 h a night, 5 h over 5 school nights.
5. Bedtime that closes the gap: 6:30 AM – 8 h – 30 min = 10:00 PM.

Weekly deficit uses 5 school nights. The weekend comparison subtracts the school-day wake-up time from your weekend wake-up time. To turn a wake-up time into bedtimes that follow sleep cycles, use the bedtime calculator.

A 15-year-old starts school at 7:30 AM, needs 60 minutes to get ready and travel, turns the lights out at 11:00 PM and takes about 30 minutes to fall asleep. At weekends the wake-up is 10:00 AM.

Part of the reason is biology, not laziness. The American Academy of Pediatrics lists biological changes in sleep associated with puberty, along with lifestyle choices and academic demands, as factors that make it harder for middle and high school students to get enough sleep.

The American Academy of Sleep Medicine describes delayed sleep-wake phase disorder as a body clock that runs two or more hours later than usual social times. It says the condition is much more common in teens and young adults, with about 7% to 16% of them possibly affected, and that once asleep, sleep is generally normal. The signs are trouble falling asleep until late at night and trouble getting out of bed for school.

A teen who cannot fall asleep before midnight and is exhausted every morning should talk to a doctor. The circadian rhythm calculator shows body clock type.

The AAP policy statement on school start times for adolescents identifies earlier start times, meaning before 8:30 AM, as a key modifiable contributor to insufficient sleep and to circadian rhythm disruption in middle and high school students. It reports that delaying start times is an effective countermeasure to chronic sleep loss, and urges schools to aim for start times that let students get 8.5 to 9.5 hours of sleep.

Families rarely control the bell time, but each 30-minute shift is worth 30 minutes of sleep a night.

Sleeping much later on days off is a mismatch between the school-day body clock and the weekend one. In plain words, if the weekend wake-up is 3 hours later than the school-day wake-up, the body is being asked to feel like it moved 3 time zones west every Saturday and back east every Monday. This is often called social jetlag.

The NHLBI notes that sleeping more on days off might be a sign of not getting enough sleep, and that although extra sleep may help you feel better, it can upset the body sleep-wake rhythm. A gap of several hours is a signal to look at the school-night bedtime first. Any sleep calculator on this site starts from the same idea: fix the wake-up time, then plan the bedtime.

Time to fall asleep and time to get ready and travel move the result most, so enter real figures rather than hoped-for ones. Sleep quality is not counted: loud snoring, pauses in breathing or constant daytime sleepiness need a doctor even when the hours look fine.

• Move bedtime in small steps. Go 15 minutes earlier every few nights until you reach the closing bedtime shown by the calculator.
• Keep the wake-up time steady, including weekends, within an hour or so if possible.
• Get morning daylight. The AASM notes that too little morning sunlight and too much bright evening light may make a delayed body clock worse.

• Parents checking whether a school-night routine leaves enough sleep.
• Teens who want a bedtime that fits their own school start time.

The usual errors are counting time in bed as sleep, using weekend sleep as the normal, and ignoring the morning routine, which sets the wake-up time as much as the bell does.

The arithmetic is exact for the times you enter. Real sleep varies from night to night, so treat the result as a planning estimate.

Teens aged 13 to 18 need 8 to 10 hours of sleep a day, according to the NHLBI, with the ranges endorsed by the American Academy of Pediatrics.

Children aged 6 to 12 need 9 to 12 hours a day, and the calculator measures the deficit against the 9-hour minimum.

Work out the sleep a school night gives, then subtract it from the bottom of the range. Seven hours against an 8-hour minimum is a 1-hour nightly deficit, or 5 hours over a 5-night school week.

Count back from the wake-up time: the wake-up time minus 8 hours minus the minutes to fall asleep. For a 6:30 AM wake-up and 30 minutes to fall asleep that is 10:00 PM.

A short lie-in is common, but a wake-up several hours later than on school days can unsettle the body clock. A gap of several hours is a reason to move the school-night bedtime earlier.

The American Academy of Pediatrics urges middle and high schools to start no earlier than 8:30 AM so students can get enough sleep, though many schools start earlier.

Yes. Switch the age group to Child 6-12, which uses the 9 to 12 hour range. For under 6, use the baby sleep calculator or the sleep by age tool.

See a doctor if a teen cannot fall asleep until very late despite a good routine, is sleepy all day, snores loudly, or struggles to stay awake in class or while driving.

• NHLBI: How much sleep is enough (teens 8 to 10 h, children 6 to 12 years 9 to 12 h; days-off sleep)
• AAP policy: School start times for adolescents (PMID 25156998) (Pediatrics 2014, PMC copy; before 8:30 am; 8.5 to 9.5 h)
• AASM Sleep Education: Delayed sleep-wake phase (late body clock; common in teens)
• MedlinePlus: Healthy sleep (sleep by age)