Sleep
Bedtimes worked back from 32 wake-up times and wake times worked forward from 28 bedtimes, at quarter-hour steps. The arithmetic is the same one every sleep calculator does. What is different here is that each page says what it assumes, because the ninety-minute cycle those calculators are built on is a population average and not a fact about your night.
Start from your alarm
- Waking at 5:00 am Asleep by 10:00 pm for seven hours, 8:00 pm for nine
- Waking at 5:30 am Asleep by 10:30 pm for seven hours, 8:30 pm for nine
- Waking at 6:00 am Asleep by 11:00 pm for seven hours, 9:00 pm for nine
- Waking at 6:30 am Asleep by 11:30 pm for seven hours, 9:30 pm for nine
- Waking at 7:00 am Asleep by 12:00 am for seven hours, 10:00 pm for nine
- Waking at 7:30 am Asleep by 12:30 am for seven hours, 10:30 pm for nine
- Waking at 8:00 am Asleep by 1:00 am for seven hours, 11:00 pm for nine
- Waking at 8:30 am Asleep by 1:30 am for seven hours, 11:30 pm for nine
- Waking at 9:00 am Asleep by 2:00 am for seven hours, 12:00 am for nine
Every wake time
- 4:00 am
- 4:15 am
- 4:30 am
- 4:45 am
- 5:00 am
- 5:15 am
- 5:30 am
- 5:45 am
- 6:00 am
- 6:15 am
- 6:30 am
- 6:45 am
- 7:00 am
- 7:15 am
- 7:30 am
- 7:45 am
- 8:00 am
- 8:15 am
- 8:30 am
- 8:45 am
- 9:00 am
- 9:15 am
- 9:30 am
- 9:45 am
- 10:00 am
- 10:15 am
- 10:30 am
- 10:45 am
- 11:00 am
- 11:15 am
- 11:30 am
- 11:45 am
Or start from your bedtime
- 8:00 pm
- 8:15 pm
- 8:30 pm
- 8:45 pm
- 9:00 pm
- 9:15 pm
- 9:30 pm
- 9:45 pm
- 10:00 pm
- 10:15 pm
- 10:30 pm
- 10:45 pm
- 11:00 pm
- 11:15 pm
- 11:30 pm
- 11:45 pm
- 12:00 am
- 12:15 am
- 12:30 am
- 12:45 am
- 1:00 am
- 1:15 am
- 1:30 am
- 1:45 am
- 2:00 am
- 2:15 am
- 2:30 am
- 2:45 am
How much sleep each age needs
| Age | Per day | What it covers |
|---|---|---|
| Babies, 4 to 12 months | 12 to 16 hours | Including daytime naps |
| Toddlers, 1 to 2 years | 11 to 14 hours | Including daytime naps |
| Preschoolers, 3 to 5 years | 10 to 13 hours | Including daytime naps |
| Children, 6 to 12 years | 9 to 12 hours | Night sleep |
| Teenagers, 13 to 18 years | 8 to 10 hours | Night sleep |
| Adults, 18 and over | 7 or more hours | Night sleep |
- How much sleep does a baby need? 12 to 16 hours
- How much sleep does a toddler need? 11 to 14 hours
- How much sleep does a preschooler need? 10 to 13 hours
- How much sleep does a child of primary-school age need? 9 to 12 hours
- How much sleep does a teenager need? 8 to 10 hours
- How much sleep does an adult need? 7 or more hours
The parts worth understanding
- What a sleep cycle actually is Stages, why the night is not made of identical cycles, and what that does to alarm timing
- When to stop drinking coffee A five-hour half-life means an afternoon coffee is still a quarter present at midnight
Common questions
- What time should I go to bed to wake up at 6 am?
- Asleep between 9 pm and 11 pm for nine to seven hours, so in bed from about 8:45 pm to 10:45 pm allowing fifteen minutes to fall asleep.
- How much sleep do adults need?
- Seven or more hours a night, according to the American Academy of Sleep Medicine consensus statement. It gives a floor rather than a range and deliberately does not endorse eight as a target.
- How long is a sleep cycle?
- About 90 minutes on average, but genuinely 70 to 120 in practice, and the cycles lengthen through the night. That is why cycle-aligned alarm times are a rough target rather than a schedule.
Sources
- Recommended Amount of Sleep for a Healthy Adult: A Joint Consensus Statement — Watson et al., Sleep 38(6) / Journal of Clinical Sleep Medicine, 2015
- Recommended Amount of Sleep for Pediatric Populations: A Consensus Statement — Paruthi et al., Journal of Clinical Sleep Medicine 12(6), 2016
- Normal Human Sleep: An Overview — Carskadon & Dement, Principles and Practice of Sleep Medicine, 6th ed., 2017