How Much Sleep Do I Need? Sleep Calculator by Age

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Formula at a glance

Sleep Needs by Age Calculator: Latest bedtime — Wake-up time − minimum hours − time to fall asleep. Example: Adult waking at 6:30 AM → Recommended sleep: 7–9 hours a day — How the Sleep Needs by Age Calculator works: Latest bedtime — Wake-up time − minimum hours − time to fall asleep

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📘 About the How Much Sleep Do I Need? Sleep Calculator by Age

Babies need 12–17 hours of sleep a day, school children 9–12, teenagers 8–10 and adults 7–9. These ranges come from the American Academy of Sleep Medicine and the US National Sleep Foundation, based on hundreds of studies of health and performance.

Enter the age and wake-up time. The calculator shows the healthy range, the latest bedtime that still gives enough sleep, an ideal bedtime window, and for adults the bedtimes for 5 or 6 full 90-minute sleep cycles.

🧮 Formula

Latest bedtime

Wake-up time − minimum hours − time to fall asleep

Cycle bedtime

Wake-up time − cycles × 90 min − time to fall asleep

✏️ Worked examples

Adult waking at 6:30 AM

You enter
Age	30 years
Plus months (for babies)	0 months
Wake-up time	6:30 AM
Minutes to fall asleep	15 min
Hours you sleep now (optional)	6 hours

You get
Recommended sleep	7–9 hours a day
Age group	Adult (18–64 years)
To wake at 6:30 AM, go to bed by	11:15 PM at the latest
Ideal bedtime window	10:15 PM – 10:45 PM
You sleep 6 hours	about 1 hours too little
6 full 90-minute sleep cycles	bed at 9:15 PM (9 h of sleep)
5 full 90-minute sleep cycles	bed at 10:45 PM (7.5 h of sleep)

7–9 hours a day; bed by 11:15 PM at the latest.

10-year-old waking at 6:45 AM

You enter
Age	10 years
Plus months (for babies)	0 months
Wake-up time	6:45 AM
Minutes to fall asleep	15 min

You get
Recommended sleep	9–12 hours a day
Age group	School child (6–12 years)
To wake at 6:45 AM, go to bed by	9:30 PM at the latest
Ideal bedtime window	8:00 PM – 9:00 PM

9–12 hours a day.

🧭 How to use this calculator

What you enter

Age (years)
Plus months (for babies) (months)
Wake-up time
Minutes to fall asleep (min)
Hours you sleep now (optional) (hours)

What you get

Recommended sleep
Age group
To wake at 6:30 AM, go to bed by
Ideal bedtime window
6 full 90-minute sleep cycles
5 full 90-minute sleep cycles

💡 Sleep better tonight

Keep the same wake-up time every day.
Get daylight in the morning.
No caffeine after 2 PM.
Keep screens out of bed for the last 30–60 minutes.

❓ Frequently asked questions

How many hours of sleep does a teenager need?

8–10 hours a night. Most teenagers get less because their body clock shifts later while school starts early.

Is 6 hours of sleep enough?

Not for most adults. Regularly sleeping under 7 hours is linked to weight gain, high blood pressure, low mood and poorer focus; a few people genuinely need less, but they are rare.

Do older adults need less sleep?

A little: 7–8 hours for over-65s. Their sleep is often lighter and broken, so naps and a regular routine help.

😴 How Much Sleep Do I Need? Sleep Calculator by Age