How many hours do I need?

Most adults land somewhere between seven and nine, but the range is wide and individual. A better test than the number is how you function: if you wake without an alarm most days and get through the afternoon without flagging, you're probably getting enough.

Is it bad to catch up at weekends?

A later night now and then costs little. A long lie-in costs more, because it moves your body clock and makes Sunday night harder. If you're short of sleep, going to bed earlier is a better repair than getting up later.

Do blue-light glasses help?

A Cochrane review of 17 trials found they probably make no difference to sleep quality. A time you stop using screens is worth more than any filter or tinted lens.

What about melatonin supplements?

In the UK, melatonin is a prescription medicine, and prolonged-release melatonin is licensed for adults aged 55 and over. It is not the over-the-counter sleep aid it is in some countries, and it is not part of this guide.

Should I try sleep restriction?

Not from a web page. Sleep restriction is an effective part of CBT-I, but it temporarily increases daytime sleepiness, which matters if you drive or operate machinery, and it needs proper support to do well. The Complete Guide to Insomnia explains how it works and how to access it.

Are sleep trackers worth it?

They estimate rather than measure, and they are least accurate about time spent awake — the thing that matters most if you're sleeping badly. If a score makes you anxious about sleep, that is a reason to stop looking at it.

Reset Guides · Sleep & Energy · Free · 12 min read
Last reviewed 10 October 2026

The Sleep Reset

A free, practical guide to the daily foundations of good sleep — what the evidence supports, what it doesn't, and six habits worth building in order of how much they matter.

TL;DR

Regularity is the habit with the most behind it. Going to bed and getting up at roughly the same time, weekends included, predicted long-term outcomes better than sleep duration in the largest study to compare them. That is one observational cohort, and it does not mean hours stop mattering.
Morning light sets the clock. Getting outside within an hour of waking is the cheapest way to make the evening easier.
Caffeine has a cut-off, and it depends on the dose. Work it back from your own bedtime: about nine hours for a standard cup, and over thirteen for a large or double-shot drink.
Alcohol's effect starts at around two drinks, and it lands on dream sleep rather than on how long you sleep.
Several popular rules don't survive a look at the evidence — blue-light glasses, a precise bedroom temperature, counting sleep cycles.
Foundations are not a treatment for insomnia. If you are lying awake several nights a week and it is affecting your days, section 07 is the part to read — and it is worth raising with a GP now rather than waiting.

01Start with regularity

Most sleep advice is about the hours — getting your eight, catching up at weekends, counting what you're owed. The strongest recent evidence points somewhere else. A study of 60,977 UK adults who wore wrist trackers for a week found that how consistent their sleep timing was predicted health outcomes over the following six years better than how long they slept. The most regular sleepers had notably lower mortality than the least regular, and once regularity was in the model, adding sleep duration told you nothing extra.

That is a strong finding, and it needs holding accurately. It is an observational study in mostly older adults, so it shows an association rather than proving that fixing your timings extends your life. It also measures long-term health, not how rested you feel tomorrow morning. What makes it useful anyway is that regularity is the one sleep habit you can control directly, it costs nothing, and nothing else in the research comes with this much behind it.

In practice, regularity means one thing above all: a consistent time of getting up. Your wake time is the anchor, because it is the one you can set. Bedtime drifts with the evening, but the alarm doesn't have to, and a steady wake time gradually pulls the rest into line.

The same amount of sleep, two different weeks. It's the shift, not the total, that the evidence points at.

If shift work or regular travel makes a fixed wake time impossible, this guide will only take you so far. A body clock being moved by a rota or a time zone is a different problem from one that drifts at weekends, and it needs different handling — the circadian section of our Complete Guide to Insomnia covers what applies when the schedule isn't yours to set.

02What is happening while you sleep

Sleep runs in repeating stretches of light sleep, deep sleep and REM — the stage where most dreaming happens. Deep sleep is weighted towards the first half of the night and REM towards the second, which is why a late night costs you proportionally more dreaming and an early start costs you less deep sleep than you'd expect. Each run through takes somewhere between 90 minutes and two hours, and the pattern shifts as the night goes on.

Deep sleep comes early in the night, dreaming comes later — which is why a late night and an early start cost you different things.

That is roughly all you need. What you do not need is a target number of cycles, a breakdown of your stage percentages, or a score out of a hundred from a wrist tracker. Those devices are good at spotting that you're asleep and poor at spotting when you're awake, which means the number they give you is least reliable about the thing you most want to know. Chasing a better one is its own problem.

03What's keeping you awake

What it is	What the evidence shows	What to do
Irregular timing	The best-supported influence on long-term outcomes, ahead of duration	Fix your wake time first; let bedtime follow
Caffeine too late	Across 24 studies: 45 minutes less sleep and 7% lower sleep efficiency	Count back from bed: about nine hours for a standard cup, longer for a large one — see step 3
Alcohol	Reduces and delays REM sleep from roughly two drinks, worsening with more	Treat two as the point where it starts, not a safe floor
A busy mind at bedtime	Lying awake trying to sleep makes sleep less likely, not more	Give the day somewhere to go before you're in bed — step 6
A room that's too warm	Sleep efficiency drops measurably as rooms get hot	Cooler is better than warmer; there's no magic number
Screens late	Weaker than commonly claimed — see below	Set a time you stop, not a colour filter

The screens point is worth separating out, because it is the most repeated claim in sleep advice and the least supported. A Cochrane review of 17 randomised trials found blue-light filtering glasses probably make no difference to sleep quality. Melatonin suppression by bright light is real in a laboratory; a phone at normal brightness in a lit room is a long way from that. What costs you sleep is the content — something engaging keeps you up and keeps you alert — and the simple fact that the hour spent scrolling is an hour not spent asleep. A cut-off time works. Tinted glasses don't.

04The six-step Sleep Reset

1. Anchor your wake time

Pick a time you can hold seven days a week and set it. Not the time you'd like to be up on your best day — the time you can manage on an ordinary one. If weekends currently run two or three hours later, move them in stages rather than all at once — half an hour a week, until the gap is as small as you can hold seven days a week.

2. Get light in early

Daylight in the first hour after waking is what tells your body clock where the day starts, and it does more for your evening than anything you do in the evening. Ten to twenty minutes outside is enough, and an overcast British morning is still many times brighter than indoor lighting. Walk to the shop, drink your coffee by an open door, take the long way to the station.

Soft morning sunlight falling through a window onto a linen-covered table with a cup of coffee — Ten to twenty minutes of daylight early on does more for the evening than anything done in the evening.

3. Work out your caffeine cut-off

A systematic review of 24 studies put the cut-off for a standard cup of coffee at about nine hours before bed — and for a pre-workout serving, over thirteen. "Nothing after 2pm" only works if you go to bed at eleven. Work it back from your own bedtime instead.

If you go to bed at	Last coffee by
10:00pm	1:00pm
10:30pm	1:45pm
11:00pm	2:15pm
11:30pm	2:45pm
Midnight	3:15pm

Those times are based on a standard 107 mg cup. A large or double-shot coffee carries roughly twice the caffeine and needs closer to thirteen hours, so shift the whole column earlier if that is what you drink.

Tea, cola, energy drinks and dark chocolate all count. So does decaf, a little — it is not caffeine-free.

4. Be honest about the wine

Alcohol makes you drowsy and then takes the quality back later. A review of 27 studies found it delays and shortens REM sleep from around two standard drinks, getting worse with every additional one. It takes about five drinks before it measurably speeds up falling asleep, by which point the damage to the rest of the night is considerable.

What the evidence does not clearly show is an effect on your total hours or on how often you wake — those results were too uncertain to call. So the honest version is narrower than the usual warning, and more useful: alcohol is not costing you sleep so much as costing you the restorative part of it.

5. Make the bedroom somewhere you fall asleep

Dark and quiet are worth getting right: blackout curtains or an eye mask, earplugs or something with a steady hum if noise is the problem. On temperature, be sceptical of precise numbers. The best real-world study — home sensors and wearables, tracked over months — found sleep most efficient between 20°C and 25°C, which is warmer than the figure usually quoted, and it also found large differences between individuals. Cooler is generally better than warmer. Beyond that, your own comfort is the better guide than anyone's recommended range.

One thing with good evidence behind it: a warm bath or shower, one to two hours before bed, cuts around ten minutes off the time it takes to fall asleep. The warmth brings blood to the skin, and the drop in core temperature afterwards is the signal your body reads as bedtime.

6. Give the day somewhere to go

The most common reason people can't sleep is not light or caffeine. It is arriving in bed with the day still running. A short wind-down works better than a long one because you'll keep it up: twenty minutes of something undemanding, with the lights lower than you think they need to be.

Writing tomorrow's list before you go up is the specific habit worth trying. Most bedtime thinking is rehearsal — holding onto things because you're afraid of forgetting them — and a list on paper takes that job away. If worry rather than planning is the problem, the same thing applies earlier in the evening: a set fifteen minutes to think about it deliberately, well before bed, so it has somewhere to live other than eleven o'clock at night.

05What a week looks like

Nothing here needs buying. The point of writing it out is that it shows how little changes.

	Morning	Daytime	Evening
Weekdays	Same alarm. Outside within the hour	Last coffee at your cut-off	Lights down from 10. List written. Bed at a similar time
Saturday	Alarm within an hour of weekdays	A walk if you can	Later night is fine — hold the morning
Sunday	Same alarm again	Daylight early	Normal wind-down, ready for Monday

The Saturday row is the one that matters. A late night now and then costs you very little if the wake time holds. It's the lie-in that undoes the week.

A neatly made bed with pale linen in a cool, dim bedroom — Dark, quiet and not too warm — the room only has to make falling asleep easy.

06Track it for four weeks

Two weeks of notes will tell you more than any tracker, and a short sleep diary is what a clinician would ask for anyway — so if you do end up seeking help, you arrive with the thing they need.

Sleep diary

Night	Lights out	Asleep around	Awake in the night	Up at	How the day felt (1–5)
Mon
Tue
Wed
Thu
Fri
Sat
Sun

Estimates are fine. Do not clock-watch to fill it in — that defeats the purpose.

The six habits

Habit	M	T	W	T	F	S	S
Up at my anchor time
Daylight within the hour
Last caffeine before cut-off
No alcohol, or one drink
Wind-down and list
Dark, quiet, not too warm

Four or five ticks a row is a good week. Aiming for seven turns the guide into one more thing to fail at, which is the opposite of useful.

07When the foundations aren't the answer

Everything above is for people who sleep reasonably and want to sleep better. It is not a treatment for insomnia disorder, and the difference is worth knowing.

Persistent insomnia is sustained by different mechanisms than the ones this guide addresses — extra time in bed, a learned association between the bedroom and being awake, and the effort of trying to sleep — and habit advice does not reach them. The recommended treatment is CBT-I, which has considerably better evidence behind it than anything on this page. Our Complete Guide to Insomnia covers what it involves and how to get it in the UK.

There is also a trap in this guide worth naming. If you find yourself checking the bedroom thermometer, calculating your caffeine window to the minute and treating every departure from the routine as a reason tonight will go badly, you have turned foundations into sleep effort, and sleep effort keeps people awake. Hold all of it loosely. These are habits, not rules.

Frequently Asked Questions

How many hours do I need?: Most adults land somewhere between seven and nine, but the range is wide and individual. A better test than the number is how you function: if you wake without an alarm most days and get through the afternoon without flagging, you're probably getting enough.
Is it bad to catch up at weekends?: A later night now and then costs little. A long lie-in costs more, because it moves your body clock and makes Sunday night harder. If you're short of sleep, going to bed earlier is a better repair than getting up later.
Do blue-light glasses help?: A Cochrane review of 17 trials found they probably make no difference to sleep quality. A time you stop using screens is worth more than any filter or tinted lens.
What about melatonin supplements?: In the UK, melatonin is a prescription medicine, and prolonged-release melatonin is licensed for adults aged 55 and over. It is not the over-the-counter sleep aid it is in some countries, and it is not part of this guide.
Should I try sleep restriction?: Not from a web page. Sleep restriction is an effective part of CBT-I, but it temporarily increases daytime sleepiness, which matters if you drive or operate machinery, and it needs proper support to do well. The Complete Guide to Insomnia explains how it works and how to access it.
Are sleep trackers worth it?: They estimate rather than measure, and they are least accurate about time spent awake — the thing that matters most if you're sleeping badly. If a score makes you anxious about sleep, that is a reason to stop looking at it.

This guide is for general information and education, not medical advice. If poor sleep is persistent or affecting your daily life, speak to your GP.

Sources

Windred DP, et al. Sleep regularity is a stronger predictor of mortality risk than sleep duration: a prospective cohort study. SLEEP 2024;47(1):zsad253.
Gardiner C, et al. The effect of caffeine on subsequent sleep: a systematic review and meta-analysis. Sleep Medicine Reviews 2023.
Gardiner C, et al. The effect of alcohol on subsequent sleep in healthy adults: a systematic review and meta-analysis. Sleep Medicine Reviews, April 2025.
Singh S, Downie LE, et al. Blue-light filtering spectacle lenses for visual performance, sleep, and macular health in adults. Cochrane Database of Systematic Reviews 2023; CD013244.pub2.
Haghayegh S, Khoshnevis S, Smolensky MH, Diller KR, Castriotta RJ. Before-bedtime passive body heating by warm shower or bath to improve sleep: a systematic review and meta-analysis. Sleep Medicine Reviews 2019;46:124.
Baniassadi A, et al. Nighttime ambient temperature and sleep in community-dwelling older adults. Science of the Total Environment 2023.
Miao A, Luo T, Hsieh B, et al. Brain clearance is reduced during sleep and anesthesia. Nature Neuroscience 2024;27:1046–1050.