How much sleep do I need?

By Vitalii Shumylo · 3 October 2026 · 7 min read

Most adults need at least 7 hours of sleep a night, and for many people the right number sits somewhere between 7 and 9. That's the range major sleep bodies agree on, but your own need is a point inside it, and the honest way to find it is to measure your sleep for a week, not to guess. If you need an alarm every morning and you're drowsy by mid-afternoon, you're probably getting less than you need.

Here's the plan: the numbers the experts use, the difference between time in bed and time asleep, how sleep debt builds, and a one-week test that ends with your own starting point.

What the guidelines say

Before you pick a number for yourself, it helps to know where the usual "7 to 9 hours" comes from. In 2015 the American Academy of Sleep Medicine and the Sleep Research Society published a consensus statement saying adults aged 18 to 60 should sleep 7 or more hours a night on a regular basis for the best health. The same year, an expert panel of the US National Sleep Foundation (Hirshkowitz and colleagues, 2015) recommended 7 to 9 hours for adults and 7 to 8 hours for people aged 65 and over. The NHS gives the same 7 to 9 hour range for adults.

Notice the wording: "7 or more", not "exactly 8". I'd treat the range as a floor and a band, not a target to hit to the minute, because people differ. A few need a little more than 9; very few healthy adults do well on less than 7 over the long run.

The guideline is a range; your job is to find where you sit inside it.

So the next question is how to measure your own sleep, and that's where most people trip over a simple detail.

Time in bed is not time asleep

The number people quote is usually the time between getting into bed and getting up. That's not the same as sleep. You take a while to drift off, you wake briefly in the night, and you might lie there for a bit after the alarm.

Sleep scientists use a measure called sleep efficiency: time asleep divided by time in bed. The National Sleep Foundation's panel on sleep quality (Ohayon and colleagues, 2017) treats a sleep efficiency of 85% or more as a sign of good sleep. So eight hours in bed can easily mean under seven hours asleep.

Try this tonight:

1. Because your memory of last night is fuzzy by lunchtime, write down three times as soon as you get up: when you went to bed, roughly when you fell asleep, and when you got up.
2. Because brief wake-ups are normal and easy to forget, add a rough total for any time you lay awake in the night.
3. Subtract the awake time from the time in bed. That's your time asleep, and it's the number that matters.

You'll see the gap straight away. If you were in bed for 8 hours and awake for 50 minutes of it, your night was about 7 hours 10 minutes of sleep.

How sleep debt builds up

Once you know your real nightly figure, the next step is to see what happens when it falls short several nights in a row. Sleep debt is the running gap between the sleep you need and the sleep you get. Lose an hour a night across a working week, and you're five hours behind by Friday.

The tricky part is that you stop noticing it. In a 2003 study in the journal Sleep, Van Dongen and colleagues kept healthy adults to six hours in bed a night for two weeks: their scores on an attention test kept getting worse, while their own sleepiness ratings rose only a little. In other words, feeling "used to it" isn't proof you're fine.

Pause and think: if you sleep 6 hours on weeknights and 9 on Saturday and Sunday, does the weekend clear the debt?

Answer: only partly. A lie-in helps you feel better, but in a 2019 study in Current Biology (Depner and colleagues), weekend recovery sleep did not prevent the effects of short weeknights on how the body handled blood sugar, and sleeping much later at weekends shifts your body clock, which makes Sunday night harder. A steadier weekday amount usually works better than a big weekend catch-up.

Sleep debt hides itself, which is why you measure it rather than trust how you feel.

Find your own number in a week

With the theory in place, let's turn it into a test you can run on yourself. The aim is a starting point, not a perfect answer.

Try this for 7 nights:

1. Because one night tells you nothing, keep a sleep diary for a full week, weekend included. Log bedtime, time to fall asleep, wake-ups, and get-up time.
2. Because a number on its own isn't the full picture, add one line each day: how alert you felt at about 3 pm, on a scale of 1 to 5.
3. Because your get-up time is usually fixed by work or school, work backwards from it. If you need 7.5 hours asleep and take about 15 minutes to drop off, lights out is roughly 7 hours 45 minutes before your alarm.
4. At the end of the week, look for the pattern: on nights with more sleep, were your afternoons better?

I'd change only one thing at a time here, usually lights-out, not wake-up time, because a fixed wake-up time is what anchors your body clock. Moving both at once makes the diary hard to read.

A fixed wake-up time plus a measured week tells you more than any chart.

Common mistake: counting time in bed as sleep

What it looks like: "I'm in bed for eight hours, so I can't be short of sleep", yet you're foggy every afternoon.

Why it happens: the clock time is easy to remember, and the time spent falling asleep or lying awake isn't.

The fix: log time asleep, not time in bed, for a week. If your efficiency is low because you lie awake for long spells, that's a different problem from not giving yourself enough time, and the insomnia module covers it.

FAQ

Is 6 hours of sleep enough?

For most adults, not regularly. The consensus guidance puts the floor at 7 hours. A small number of people seem to need less, but it's rare, and you can't tell you're one of them from how you feel alone.

Can you sleep too much?

Regularly needing well over 9 hours, or still feeling unrefreshed after long nights, is worth mentioning to a GP. It can be linked to an underlying problem rather than being the cause of anything itself.

Do naps count towards my total?

They add to your sleep over 24 hours, but they don't replace a proper night. Short naps can help; long or late ones can make the next night harder.

How much sleep do teenagers and children need?

More than adults. The US Centers for Disease Control and Prevention (CDC) gives 8 to 10 hours for 13- to 17-year-olds, and younger children need more again. The article on how sleep changes with age goes through each stage.

This is general information, not medical advice. If you're worried about your sleep, or sleepiness is affecting your driving, work or mood, talk to your GP or doctor.

Go deeper

Module 1 of "Sleep, Decoded" covers how much sleep you need, why time in bed isn't time asleep, sleep debt, and your own starting point with diary, alertness, caffeine and body-clock checks. The Bedtime calculator counts back from your get-up time to a lights-out window, and the 7-day sleep diary works out your time asleep, sleep efficiency and weekly averages for you.

Open Module 1: Your sleep, right now (free)

• Bedtime calculator - Enter the time you need to get up and how long you take to fall asleep; it counts back to a lights-out window.
• 7-day sleep diary - Log a night in about 2 minutes. It works out your time asleep, sleep efficiency and weekly averages.