Your sleep needs vary during your lifetime and by how many sleep cycles you need to feel rested.

Keeping track of your sleep schedule might not always be your top priority, but getting enough sleep is critical to your health.

The amount of sleep you get can affect everything from weight and metabolism to brain function and mood.

For many people, wake-up time remains fairly constant from day to day. The time you go to sleep, however, may vary. Knowing the specific amount of sleep you need to function at your best can help you determine what time to go to bed.

Below, you’ll learn how to calculate the best time to go to bed based on your wake time and natural sleep cycles. We’ll also offer more insight into how sleep cycles work and why sleep, or lack thereof, can affect your health.

How much sleep you need changes throughout your lifetime. Sleep guidelines can offer a place to start determining your sleep needs by providing research-backed recommendations for the ideal amount of sleep for optimal health.

The American Academy of Pediatrics and the Centers for Disease Control and Prevention (CDC) offer these general guidelines for different age groups:

Sleep guidelines by age

  • Birth to 3 months: 14 to 17 hours
  • 4 to 11 months: 12 to 16 hours
  • 1 to 2 years: 11 to 14 hours
  • 3 to 5 years: 10 to 13 hours
  • 6 to 12 years: 9 to 12 hours
  • 13 to 18 years: 8 to 10 hours
  • 18 to 64 years: 7 to 9 hours
  • 65 years and older: 7 to 8 hours

Sleep needs can still vary within the same age group.

The thing to keep in mind is how you feel when you get various amounts of sleep.

Here are a few questions to consider when evaluating your sleep needs:

  • Do I feel rested after 7 hours of sleep, or do I need at least 8 or 9?
  • Do I experience any daytime drowsiness?
  • Do I rely on caffeine to keep me going throughout the day?
  • Has my sleeping partner noticed me tossing and turning or having any sleep issues during the night?

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 Bedtime:
7.5 hours of sleep
(5 cycles) 		Bedtime:
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.

Health and mental health conditions can contribute to sleep deprivation. This can include:

Poor quality sleep can also worsen these conditions and fuel a cycle of sleeplessness.

The occasional night of poor sleep generally won’t seriously impact your health. But, experts have linked ongoing sleep deprivation to serious health consequences, including a higher risk of chronic diseases and early death.

Sleep deprivation can impact short-term and long-term physical, emotional, and cognitive health.

Physical impacts

A night of poor sleep can cause physical effects, including:

Long-term sleep deprivation can take a more severe toll on your health, leading to:

Emotional and mental health impacts

Not getting enough sleep can affect your mood.

Not getting enough sleep can lead to:

Research also suggests sleep deprivation can worsen mental health symptoms, including depression, anxiety, paranoia, and hallucinations.

Sleep deprivation has also been linked to symptoms of some mental health conditions, including:

Cognitive impacts

When you don’t get enough sleep, your brain can’t work as efficiently, and you may have trouble concentrating and remembering things.

Research suggests sleep deprivation negatively affects functions of the brain’s frontal lobe, including:

  • attention
  • alertness
  • decision making
  • judgment
  • memory
  • response

These effects can play a part in:

  • declining performance at work or school
  • changes in judgment and impulse control
  • accidents

Does your need for sleep change with age?

Your need for sleep changes with age and typically stabilizes around age 20.

As you get older, you generally need less sleep. Environmental, behavioral, and medical factors can influence how much sleep you need, and those may change throughout your life.

Why am I still tired after sleeping for 8 hours?

There are a few possible reasons you might wake up tired, even after sleeping for 8 hours. A good place to start exploring these reasons? Consider your sleep habits and sleep hygiene practices.

If you wake up tired after sleeping for 8 hours, you may need to adjust your sleep hygiene practices or treat an underlying condition. Things that could detract from quality sleep include:

  • your sleep environment
  • movement or noise from a bed partner or pet
  • sleep disorders like insomnia or sleep apnea
  • chronic pain
  • an underlying medical or mental health condition

Is it healthy to nap during the day?

Taking naps longer than 30 minutes during the day may negatively affect sleep quality at night. In a 2023 study, longer nappers who napped for longer than 30 minutes during the day had an increased risk for cardiovascular disease than people who napped for less than 30 minutes.

If you aim for 7 to 9 hours of sleep each night, a sleep calculator like the one above can help you figure out what time to go to bed based on your wake-up time.

Ideally, waking up at the end of your sleep cycle, when you’re most likely to feel rested, would be best.

Quality sleep supports good health, so if you’re having trouble falling or staying asleep, consider contacting a healthcare professional. They can help you explore the underlying causes of sleep difficulties and offer guidance.