How much deep sleep do you need?
Roughly 1 to 1.5 hours a night, a bit less after 40. That’s what healthy adults got in sleep labs. And trackers can miss 30 to 50% of it, so one other test matters more.
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How much deep sleep should you get a night?
Roughly 1 to 1.5 hours, going by sleep labs, and a bit less if you’re over 40. No UK body sets a number. The NHS says adults need 7 to 9 hours of sleep on average, but gives no figure for deep sleep.
So the best guide is what healthy people get in a sleep lab. Adults aged about 28, with 8 hours in bed, averaged 63 to 82 minutes across the groups tested.
| Who | Deep sleep a night | Study |
|---|---|---|
| Adults aged about 28, 8 hours in bed | 63 to 82 minutes on average | Chinoy 2021, US |
| Adults aged 30 or under | About 94 minutes, a typical 20.7% of the night | Mitterling 2015, Austria |
| Adults aged 31 to 40 | About 90 minutes, a typical 19.3% of the night | Mitterling 2015, Austria |
| Adults aged 41 to 50 | About 66 minutes, a typical 14.1% of the night | Mitterling 2015, Austria |
| Adults aged 51 to 60 | About 73 minutes, a typical 15.5% of the night | Mitterling 2015, Austria |
| Adults over 60 | About 69 minutes, a typical 14.9% of the night | Mitterling 2015, Austria |
Sources: Chinoy 2021; Mitterling 2015
The spread was wide. Healthy over-60s ranged from 2.4% to 35.6% of their night in deep sleep.
So check your number against your age group. Then use the daytime test below, which matters more.
When do you get deep sleep?
Mostly early in the night. Sleep runs in cycles of about 90 minutes, so you have several each night.
Most deep sleep comes in the first cycles
- 1
Falling asleep
Very light sleep, halfway between awake and asleep.
- 2
First couple of cycles
A lot of deep sleep and not much light sleep.
- 3
Later cycles
Very little deep sleep and lots of light sleep.
- 4
Morning
When you have most of your dreaming (REM) sleep.
Source: Royal College of Psychiatrists
Deep sleep is the most unconscious you get in everyday life, though your brain is still working. The Royal College of Psychiatrists says it matters for memory, mental function and the body’s repair.
A long nap may leave you groggy for a while after you wake. More in morning grogginess.
Waking at 3am? Most people wake a few times a night. That’s normal if you don’t stay awake long and you aren’t tired in the day.
If you are tired in the day, try the six NHS sleep habits below.
How much deep sleep do you need by age?
You get less as you get older, in most studies. A review of 65 studies found the share of deep sleep fell with age in adults.
Source: Mitterling 2015
Not every study agrees. A 2019 review of 169 studies found no clear change in the share of deep sleep with age. Total sleep fell by about 10 minutes a decade.
Over 60 and seeing less than you used to? That may just be your age. Compare yourself with people your age, not with a 25-year-old.
Can you trust the deep sleep number on your watch?
Not on its own. A 2021 study checked consumer sleep trackers against a sleep lab. Most missed 30 to 50% of deep sleep on average.
| What was checked | What the study found |
|---|---|
| Deep sleep spotted | Most devices missed 30 to 50% on average. |
| Total deep sleep | 3 of the 6 devices that track stages counted too much. |
| A common mistake | Deep sleep labelled as light sleep. |
Source: Chinoy 2021
They get deep sleep wrong moment to moment, so even a total that looks right can’t be trusted.
That’s why the daytime test matters more. The Royal College of Psychiatrists says to judge your sleep by how you feel in the day, not by the hours.
If you feel well, alert and rested for most of the day, on most days, you’re getting enough sleep for you. If you’re constantly tired in the day, the NHS says you probably aren’t.
For which trackers do better, see how much to trust your sleep tracker.
How can you get more deep sleep?
No NHS advice is aimed at deep sleep on its own. Start with the habits the NHS gives for better sleep.
Six NHS sleep habits to start this week
- Wake up and get out of bed at the same time every day.
- Only go to bed when you’re sleepy.
- Relax for at least 1 hour before bed, for example with a bath or a book.
- Keep your bedroom dark and quiet, with blinds, an eye mask or ear plugs if needed.
- Don’t smoke or drink alcohol, tea or coffee for at least 6 hours before bed.
- Exercise regularly in the day, but not in the 4 hours before bed.
Source: NHS: insomnia
Exercise may help a little. A review of 66 studies found a single bout of exercise had a small benefit for deep sleep.
Alcohol is the trap. Studies find it adds deep sleep in the first half of the night, then disturbs the second half. More in alcohol and sleep and when to stop caffeine.
When to speak to a GP
Go by how you feel, not by a tracker score. See a GP if:
- You’ve felt tired for a few weeks and don’t know why, or your tiredness affects your daily life.
- You feel tired and have other symptoms, such as weight loss or mood changes.
- Your breathing stops and starts in your sleep, or you make gasping, snorting or choking noises. These can be signs of sleep apnoea, when your breathing stops and starts while you sleep.
- You’ve had trouble sleeping for months, changing your habits hasn’t helped, or it makes daily life hard to cope with.
- You use any kind of sleep medicine regularly. The Royal College of Psychiatrists says to speak to your GP.
Never stop or change a prescribed medicine without your prescriber. If someone has seen you stop breathing in your sleep, the NHS says it can help to bring them with you.
A GP may offer CBT, a talking therapy that changes the thoughts and habits that keep you awake. See CBT for insomnia and how to keep a sleep diary.