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How much sleep did you get last night? What about the night before? Keeping track of your sleep schedule may not be a top priority, but getting enough sleep is critical to your health in many ways.

You may not realize it, but the amount of sleep you get can affect everything from your weight and metabolism to your brain function and mood.

For many people, wake-up time is a constant. What time you go to sleep, however, tends to vary depending on your social life, work schedule, family obligations, the newest show streaming on Netflix, or simply when you start to feel tired.

But if you know what time you have to get up, and you know you need a specific amount of sleep to function at your best, you just need to figure out what time to go to bed.

In this article, we’ll help you understand how to calculate the best time to go to bed based on your wake-up time and natural sleep cycles. We’ll also take a closer look at how your sleep cycles work and how sleep can affect your health.

How much sleep you need changes throughout your lifetime. An infant may need up to 17 hours of sleep each day, while an older adult may get by on just 7 hours of sleep a night.

But an age-based guideline is strictly that — a suggestion based on research of how much sleep you may need for optimal health as your body’s needs change.

According to the National Sleep Foundation, these are the general sleep guidelines for different age groups:

Sleep guidelines

  • Birth to 3 months: 14 to 17 hours
  • 4 to 11 months: 12 to 15 hours
  • 1 to 2 years: 11 to 14 hours
  • 3 to 5 years: 10 to 13 hours
  • 6 to 13 years: 9 to 11 hours
  • 14 to 17 years: 8 to 10 hours
  • 18 to 64 years: 7 to 9 hours
  • 65 years and older: 7 to 8 hours

Everyone’s sleep needs are different, even within the same age group. Some people may need at least 9 hours of sleep a night to feel well-rested, while others in the same age group may find that 7 hours of sleep is just right for them.

Bedtimes are based on:

  • your wake-up time
  • completing five or six 90-minute sleep cycles
  • allowing 15 minutes to fall asleep
Wake-up time Bed time:
7.5 hours of sleep
(5 cycles)
Bed time:
9 hours of sleep
(6 cycles)
4 a.m. 8:15 p.m. 6:45 p.m.
4:15 a.m.8:30 p.m.7 p.m.
4:30 a.m.8:45 p.m.7:15 p.m.
4:45 a.m.9 p.m.7:30 p.m.
5 a.m. 9:15 p.m. 7:45 p.m.
5:15 a.m. 9:30 p.m.8 p.m.
5:30 a.m. 9:45 p.m.8:15 p.m.
5:45 a.m. 10 p.m.8:30 p.m.
6 a.m. 10:15 p.m. 8:45 p.m.
6:15 a.m. 10:30 p.m.9 p.m.
6:30 a.m. 10:45 p.m.9:15 p.m.
6:45 a.m. 11 p.m.9:30 p.m.
7 a.m. 11:15 p.m. 9:45 p.m.
7:15 a.m. 11:30 p.m.10 p.m.
7:30 a.m. 11:45 p.m.10:15 p.m.
7:45 a.m. 12 p.m.10:30 p.m.
8 a.m. 12:15 a.m. 10:45 p.m.
8:15 a.m. 12:30 a.m.11 p.m.
8:30 a.m. 12:45 a.m.11:15 p.m.
8:45 a.m. 1 a.m. 11:30 p.m.
9 a.m. 1:15 a.m. 11:45 p.m.

When you fall asleep, your brain and body go through several cycles of sleep. Each cycle includes four distinct stages.

  • The first three stages are part of non-rapid eye movement (NREM) sleep.
  • The last stage is rapid eye movement (REM) sleep.

The NREM stages used to be classified as stages 1, 2, 3, 4, and REM. Now, the National Sleep Foundation classifies them this way:

  • N1 (formerly stage 1): This is the first stage of sleep, and is the period between being awake and falling asleep.
  • N2 (formerly stage 2): The onset of sleep begins at this stage as you become unaware of your surroundings. Your body temperature drops slightly, and your breathing and heart rate become regular.
  • N3 (formerly stages 3 and 4): This is the deepest and most restorative sleep stage during which breathing slows, blood pressure drops, muscles relax, hormones are released, healing occurs, and your body becomes re-energized.
  • REM: This is the final stage in the sleep cycle. It takes up about 25 percent of your sleep cycle. This is when your brain is most active and dreams occur. During this stage, your eyes move back and forth rapidly under your eyelids. REM sleep helps boost your mental and physical performance when you wake up.

It takes, on average, about 90 minutes to go through each cycle. If you can complete five cycles a night, you’d get 7.5 hours of sleep a night. Six full cycles is about 9 hours of sleep.

Ideally, you want to wake up at the end of a sleep cycle instead of in the middle of it. You usually feel more refreshed and energized if you wake up at the end of a sleep cycle.

Sleep is crucial for many reasons. A good night’s sleep:

  • regulates the release of hormones that control your appetite, metabolism, growth, and healing
  • boosts brain function, concentration, focus, and productivity
  • reduces your risk for heart disease and stroke
  • helps with weight management
  • maintains your immune system
  • lowers your risk of chronic health conditions such as diabetes and high blood pressure
  • improves athletic performance, reaction time, and speed
  • may lower your risk of depression

To improve your sleep health, consider the following tips.

During the day

  • Exercise regularly, but try to schedule your workouts at least a few hours before you go to sleep. Exercising too close to bedtime may lead to interrupted sleep.
  • Increase your exposure to sunlight or bright lights during the day. This can help maintain your body’s circadian rhythms, which affect your sleep-wake cycle.
  • Try not to take long naps, especially late in the afternoon.
  • Try to wake up at the same time each day.

Before bed

  • Limit alcohol, caffeine, and nicotine in the evening. These substances have the potential to interrupt your sleep, or make it difficult to fall asleep.
  • Switch off electronics at least 30 minutes before bedtime. The light from these devices can stimulate your brain and make it harder to fall asleep.
  • Get into the habit of a relaxing routine before bedtime, like taking a warm bath or listening to soothing music.
  • Turn down the lights shortly before bedtime to help your brain understand that it’s time to sleep.
  • Turn down the thermostat in your bedroom. According to the National Sleep Foundation, 65°F (18.3°C) is an ideal sleeping temperature.

In bed

  • Avoid looking at screens like the TV, your laptop, or phone once you’re in bed.
  • Read a book or listen to white noise to help you relax once you’re in bed.
  • Close your eyes, relax your muscles, and focus on steady breathing.
  • If you’re unable to fall asleep, get out of bed and move to another room. Read a book or listen to music until you start feeling tired, then go back to bed.

If you’re aiming for 7 to 9 hours of sleep each night, a sleep calculator can help you figure out what time to go to bed based on your wake-up time. Ideally, you’ll want to wake up at the end of your sleep cycle, which is when you’re most likely to feel the most rested.

A good night’s sleep is essential to good health. If you’re having trouble falling asleep or staying asleep, consider talking to your doctor. They can help determine if there’s an underlying cause.