A 15-year-old needs 8 to 10 hours of sleep per night, so the right bedtime depends on when they have to wake up. If your teen wakes at 6:30 a.m. for school, they should be asleep by 10:30 p.m. at the latest, and ideally by 8:30 p.m. to get the full 10 hours. For most families, a bedtime between 9:00 and 10:00 p.m. hits the realistic sweet spot.
How to Calculate Your Teen’s Bedtime
The American Academy of Sleep Medicine recommends 8 to 10 hours of sleep for teenagers aged 13 to 18. To find the right bedtime, start with your teen’s wake-up time and count backward. The average U.S. public high school starts at 8:00 a.m., which means most teens need to be up by 6:30 or 7:00 a.m. to get ready and commute. In states like Louisiana and Massachusetts, schools start as early as 7:30 a.m., pushing wake-up times closer to 6:00 a.m.
Here’s what that looks like in practice:
- 6:00 a.m. wake-up: Bedtime between 8:00 and 10:00 p.m.
- 6:30 a.m. wake-up: Bedtime between 8:30 and 10:30 p.m.
- 7:00 a.m. wake-up: Bedtime between 9:00 and 11:00 p.m.
These times mean asleep, not just in bed. Most people need 10 to 20 minutes to fall asleep, so your teen should be in bed with the lights off at least 15 minutes before the target. If your teen needs to be asleep by 10:00 p.m., “bedtime” really means 9:40 or 9:45.
Why Your Teen Wants to Stay Up Late
If your 15-year-old insists they aren’t tired at 10:00 p.m., they’re probably telling the truth. During puberty, the brain’s internal clock shifts later. The body releases its sleep-signaling hormones on a delayed schedule compared to younger kids or adults, so teens genuinely don’t feel sleepy until later in the evening. This isn’t laziness or defiance. It’s a well-documented biological change.
On top of that, the pressure to sleep builds more slowly in older adolescents than it does in younger children. A 10-year-old who’s been awake since 7:00 a.m. will feel noticeably drowsy by 9:00 p.m. A 15-year-old with the same wake-up time can stay alert considerably longer because their brain accumulates sleep pressure at a slower rate. This combination of a later internal clock and slower buildup of tiredness is why so many teens drift toward midnight bedtimes when left to their own schedule.
The problem is that school start times don’t shift to match. Your teen’s biology says “stay up late,” but the alarm clock still goes off early, and that gap is where sleep deprivation happens.
What Happens When Teens Don’t Get Enough Sleep
Regularly sleeping fewer than 8 hours carries real consequences. The American Academy of Sleep Medicine links insufficient teen sleep to problems with attention, behavior, and learning. Teens who get too little sleep also face higher risks of obesity, diabetes, high blood pressure, and depression. Perhaps most concerning, insufficient sleep in teenagers is associated with increased risk of self-harm, suicidal thoughts, and suicide attempts.
The physical effects are surprisingly direct. Sleep-deprived teens tend to eat more calories, particularly after dinner, without increasing their physical activity. Over time, this shifts body composition toward more fat and a higher BMI. The hormonal disruptions from short sleep also change how the body processes sugar, setting the stage for metabolic problems that can persist into adulthood.
Daytime fatigue takes a toll on school life too. Teens who start school earlier and have longer school days report more sleep disturbances and greater daytime impairment. Screen time at bedtime makes things worse: adolescents who use screens before sleep show higher levels of daytime fatigue compared to those who don’t.
Weekend Catch-Up Sleep Doesn’t Fix It
Many families assume that sleeping in on Saturday and Sunday makes up for short sleep during the week. Research suggests otherwise. A study published in Current Biology found that people who cut their sleep by five hours during the week and then slept extra on weekends still experienced excess calorie intake, reduced energy expenditure, weight gain, and harmful changes in how their bodies handled insulin. On paper, the sleep debt was repaid, but their bodies showed damage similar to people who stayed sleep-deprived straight through the weekend.
This means a consistent bedtime matters more than occasional long sleeps. Getting 6 hours on school nights and 11 on weekends is not equivalent to getting 9 hours every night.
Practical Ways to Make Earlier Bedtimes Work
Given that your teen’s biology is pushing them to stay up late, you’ll likely need to set up their environment and habits to counteract that pull. The goal is to make falling asleep at the target time physically easier.
Keep the bedroom cool. The recommended sleeping temperature is 60 to 67°F (15 to 19°C). Anything above 70°F makes waking up during the night more likely. A cool, dark, quiet room signals the brain that it’s time to wind down.
Set a screen cutoff time at least 30 to 60 minutes before bed. The light from phones and laptops suppresses the same sleep signals that are already delayed in teens, pushing their internal clock even later. This is one of the most effective single changes a family can make. If your teen uses their phone as an alarm, have them place it across the room or switch to a standalone alarm clock.
Consistency is the most powerful tool you have. Going to bed and waking up at roughly the same time every day, including weekends, helps the internal clock stabilize. You don’t need to be rigid about it. Staying up an hour later on Friday night won’t cause problems. But a two or three-hour swing between weekday and weekend schedules effectively gives your teen jet lag every Monday morning.
Physical activity during the day helps teens fall asleep faster at night, but intense exercise within a couple of hours of bedtime can have the opposite effect. If your teen has late sports practices, they may need a longer wind-down period before bed.
Finally, be realistic. If your teen needs to wake at 6:30 a.m., getting 10 hours means being asleep by 8:30 p.m., which is impractical for most high schoolers with homework, activities, and social lives. Aim for at least 8.5 to 9 hours as a workable target, and treat 8 hours as the hard floor. A 15-year-old waking at 6:30 a.m. should have lights out by 9:45 to 10:00 p.m. at the very latest.