How much sleep do you need? The number, and how to find your own
Adults need 7 hours or more, but that is a floor, not a target. What research says about 6 hours, 9 hours, weekend lie-ins, and finding your own number.
How much sleep do you need at your age?
Expert panels have turned thousands of studies into these numbers. For adults, the American Academy of Sleep Medicine and the Sleep Research Society asked 15 experts to review 5,314 scientific articles. Their answer for ages 18 to 60: 7 hours or more per night, on a regular basis.[1] The academy’s panel for children reviewed another 864.[2]
| Age | Recommended sleep per 24 hours |
|---|---|
| 4 to 12 months | 12 to 16 hours, naps included[2] |
| 1 to 2 years | 11 to 14 hours, naps included[2] |
| 3 to 5 years | 10 to 13 hours, naps included[2] |
| 6 to 12 years | 9 to 12 hours[2] |
| 13 to 18 years | 8 to 10 hours[2] |
| Adults | 7 hours or more[1]; the US National Sleep Foundation says 7 to 9[7] |
| 65 and older | 7 to 8 hours, according to the National Sleep Foundation[7, 8] |
Both academy panels add the same caveat: how much sleep a person needs varies, shaped by genes, behaviour, health and surroundings.[1, 2] A range is the honest answer. The next question is where in that range you fall.
Why 7 hours is a floor, not a target
The adult recommendation says 7 hours or more, and the “or more” matters. A study from Japan shows why.[3]
Fifteen healthy men aged 20 to 26 first tracked their sleep at home: about 7.4 hours a night on average, which meets the recommendation. None of them was aware of a problem, such as feeling sleepy or short of sleep. Then they spent nine nights in a sleep lab with 12 hours in bed each night.[3]
On the first night they slept 10.6 hours, more than 3 hours longer than at home. Over the following nights their sleep shrank again and levelled off from about the fourth night, at an average of 8.4 hours. The researchers read that as the men’s actual need, and the gap to their sleep at home, about an hour a night, as a sleep debt they had not noticed. Thirteen of the 15 slept less at home than their estimated need.[3]
The estimates differed from man to man, from 7.3 to 9.3 hours. Even the lowest was above 7.[3]
“I’m fine on 6 hours”
Maybe. But feeling fine is exactly what short sleep makes hard to judge.
In a US lab study, healthy adults aged 21 to 38 were randomly given 4, 6 or 8 hours in bed every night for two weeks (in bed, not all of it asleep). Those with 6 hours or less got worse on every test, and the deficits kept adding up day after day. By the end, they matched the deficits of up to two nights without any sleep at all.[4]
Their own sleepiness ratings told a different story. They rose in the first days, then only a little more. The researchers concluded that the participants were largely unaware of their growing deficits.[4]
What about people who truly need little sleep? They exist, but the evidence is thin. The best-known gene for it was found in two people of one small family, and then studied in mice.[9] The National Sleep Foundation’s panel puts it plainly: sleeping far outside the recommended range is rare.[7]
Can you sleep too much?
Population studies do link long sleep to a shorter life. A meta-analysis of 16 studies with 1.38 million people found that short sleepers (usually under 7 hours) had a 12% higher risk of dying during the follow-up years, and long sleepers (usually over 8 or 9 hours) a 30% higher risk, compared with people who slept 7 to 8 hours.[5]
These are associations, built on what people said in a questionnaire. For short sleep, researchers have described several ways it could cause harm. For long sleep, the review found no study showing a way it could. Depression, undiagnosed illness, little physical activity and poor general health all go together with long sleep and may explain the link.[5]
The sleep societies are careful here. More than 9 hours a night may be appropriate for young adults, for people recovering from sleep debt and for people who are ill; for everyone else, it is uncertain whether it carries any risk.[1] Regularly sleeping far outside the recommended range can be a sign of a health problem.[7] If you are worried that you sleep too much or too little, the advice is to talk to a doctor.[1]
One more nuance, because the research is not as uniform as a single number suggests. The same review found no evidence that sleeping 6 to 8 hours is harmful.[5] It measured risk of death over years, though, not how well you think the next day. In the lab, 6 hours a night already cost something.[4]
Can you catch up at the weekend?
A US lab study tested it with 36 young adults, men and women. One group slept 5 hours a night for a five-day “workweek”, then could sleep as long as they liked over the weekend, then went back to short nights.[6]
On Friday and Saturday they slept about 3 hours more than usual in total. On Sunday night, with an early Monday alarm ahead, they slept less. Over the whole weekend, that left about 1.1 extra hours against more than 12 hours lost during the week.[6]
Once the short nights resumed, the weekend group’s body clocks ran later, they ate more after dinner and gained weight, and their insulin sensitivity (how well the body handles blood sugar) fell by 9 to 27%, depending on where it was measured. The researchers’ conclusion: weekend recovery sleep is not an effective way to prevent these effects of short sleep.[6]
That body clock shift matters for anyone who gets up early. Waking during your body’s biological night makes the grogginess after waking heavier,[10] which is the subject of our article on sleep inertia.
How to find your own number
The Japanese method, nine nights with 12 hours in bed, is not something you can do at home. But the researchers point to a simpler sign: the more someone slept on the first free night, the bigger their sleep debt turned out to be. They compare it to catching up on sleep at the weekend.[3]
From that, a rough home version. To be clear, this is our simplification of the study, not a tested method:
- Pick at least a week without an alarm, such as a holiday.
- Go to bed at the same time every night and wake up on your own.
- Ignore the first few nights. In the lab, sleep took about four nights to level off.[3]
- Average the nights after that. It is a rough guide to what your body asks for.
If your number lands far outside the ranges in the table, talk to a doctor about it.[1]
