To make your bedroom darker, work from the biggest light source down: cover the window properly (blackout curtains, a blind, or both), then deal with the light that leaks around the edges, then switch off or cover the small electronic lights inside the room. If the window cannot be fixed, or you share a room with someone on a different schedule, a good sleep mask does the same job for a few pounds.
That is the short answer. The longer one is worth reading, because most bedrooms that feel "dark enough" are not, and the difference shows up as lighter sleep and early waking rather than anything dramatic.
Why darkness matters more than it seems
Your eyes contain light-sensitive cells that have nothing to do with seeing. They report the brightness of your surroundings to the part of the brain that runs your body clock. When it is dark, the brain releases melatonin, the hormone that signals night to the rest of the body. When light reaches those cells, melatonin is held back.
This works through closed eyelids. A study by Gooley and colleagues (2011) found that ordinary room lighting in the evening delayed and shortened melatonin release in most people. Street light through a thin curtain is dimmer than that, but it is there all night, and in the early hours, when sleep is naturally lighter, even modest light makes it easier to wake and harder to drift back off.
Then there is dawn. In June, the sky over much of the UK starts to lighten before 4:30am. If your curtains let that in, your body clock gets a "morning" signal hours before you need one, which is one reason waking too early is so common in summer.
In short: Light through closed eyelids still reaches your body clock. A darker room means deeper sleep in the early hours and fewer early wakings, especially in summer.
Do a two-minute light audit
Tonight, turn everything off, lie in bed, wait a minute for your eyes to adjust, and look around. You are checking three things.
The window. Is there a glow through the fabric? Light down the sides or over the top of the curtain? A bright line under a blind?
Inside the room. Count the LEDs: phone charger, TV standby, smoke alarm, extension lead switch, smart speaker, air purifier, bedside clock. Each is small, but a blue or white LED at eye level is surprisingly bright in a dark room.
The door. A landing light left on for children, or a hallway light on a sensor, will put a strip of light under the door.
Now you know what you are dealing with. Fix in order of size.
Free and nearly free fixes
- Switch off standby lights at the wall. A single extension lead with a switch turns several off at once. For anything that must stay on, a small square of black electrical tape or a "light dimming sticker" over the LED costs pennies.
- Turn the clock away. Or replace a bright LED clock with one that has a dim setting or a display that only lights on touch.
- Charge your phone outside the bedroom, or at least face down. This also removes a temptation, which helps in its own right; there is more on that in our guide to screens before bed.
- Close the curtains properly. Overlap them in the middle and tuck the edges behind the radiator or against the wall. Curtain clips or a couple of clothes pegs close a central gap.
- Draught excluder along the door. A cheap fabric one blocks the strip of landing light as well as the draught.
For a lot of bedrooms, this is enough. If the window is still glowing, move on.
Fixing the window
Blackout curtains
Blackout curtains are the standard answer for UK bedrooms, and a good pair genuinely blocks light through the fabric. What they do not do, on their own, is block the light that comes around the edges. To get the most from them:
- Choose a pole or track that extends 15–20cm beyond the window frame on each side, so the curtains overlap the wall.
- Choose curtains that are generously wide and long enough to reach the sill or below.
- Consider a wrap-around track or a pelmet to close the gap at the top.
The thermal variety also helps keep the bedroom cooler in summer and warmer in winter, which matters more than you might expect for bedroom temperature.
Blackout blinds
A blind sits closer to the glass, so it stops more of the light before it enters the room. Roller blinds inside the recess leave a small gap at each side; a blind fitted outside the recess, or a blackout roller behind curtains, deals with most of that. Combining a blind and curtains is the closest most people get to a hotel-dark room.
Renters' options
If you cannot drill, there are no-drill blinds that clip onto the window frame or attach with suction cups, and portable blackout sheets that stick to the glass. They are not always elegant, but they work, they come with you when you move, and they leave no marks. Tension rods inside the recess can also hold a lightweight blind or curtain without a single screw.
When the window is not the answer
Some situations are easier to solve from the eyes rather than the room:
- Your partner reads in bed, or gets up at 5am and needs the light on.
- You work shifts and sleep in the daytime.
- You share a room, or you travel often.
- The bedroom has a large window, a skylight, or a glazed door that would be expensive to cover.
A sleep mask blocks light regardless of where it comes from. The two main things that make a mask work are fit around the nose, where most light leaks in, and comfort, because a mask that presses on the eyes or slides off at 3am gets abandoned. Contoured masks with raised eye cups solve both for a lot of people. The guide to sleep masks versus blackout curtains weighs the two approaches in more detail.
Three ways to get the room dark
Curtains for the window, a no-drill blind if you rent or have gaps, and a mask if the light is not something you can control.
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Thermal blackout curtains (eyelet)
Example: Various UK retailers' own brands
Blackout curtains use a dense or coated backing to block light. Thermal versions are also marketed for insulation, which can help in winter and keep rooms slightly cooler in summer when closed during the day.
- Best for
- Bedrooms with street lights or early summer dawn
- Key feature
- Multi-layer or coated fabric marketed to block most light and reduce heat loss
- Why it may help
- Curtains address the room rather than the person, so they help everyone in the bed and do not need to be worn.
- Worth knowing
- Light still leaks around the edges and top unless the curtains overlap the frame generously; measure carefully.
No-drill blackout blind
Example: Various (temporary or suction-fit blinds)
Portable or no-drill blackout blinds attach with suction cups or tension fittings and are marketed for rented homes and travel. Some are cut to size.
- Best for
- Renters, travel cots, and windows where curtains leave gaps
- Key feature
- Fits inside the window recess without drilling
- Why it may help
- Fitting inside the recess blocks the edge glow that curtains let through. Combined with curtains, the room can get very dark.
- Worth knowing
- Suction fittings may need re-fixing; less tidy-looking than fitted blinds.
Contoured (3D) sleep mask
Example: Manta Sleep Mask
A contoured mask has raised eye cups so the fabric does not press on your eyelids, which many people find more comfortable and which allows the eyes to move freely in REM sleep. Manta's version is marketed with adjustable eye cups and a wide, flat strap designed to reduce light leaks.
- Best for
- Side sleepers and anyone who dislikes pressure on the eyes
- Key feature
- Moulded eye cups that sit around, not on, the eyes
- Why it may help
- The main failure of a cheap flat mask is light leaking in around the nose. A contoured design with an adjustable strap closes that gap for more face shapes.
- Worth knowing
- Bulkier than a flat mask, so less convenient for travel.
How dark is dark enough?
You do not need a photographic darkroom. A useful test: with the lights off and your eyes adjusted, you should struggle to see your hand in front of your face. If you can read a clock face across the room without it being lit, there is still work to do.
A few people find total darkness unsettling, and that is fine. A very dim, warm-coloured light at floor level, well away from the bed, is a reasonable compromise. If you want the evidence on sleeping with a light on, we have covered it separately.
Do not make the mornings dark too
There is a catch with a very dark bedroom. Morning light is one of the strongest signals that sets your body clock for the coming night. If your blackout blind is so effective that you wake in the dark and start the day under dim bulbs, getting outside or opening the curtains within an hour of waking is worth doing on purpose. The evening side of this, choosing warm, low lighting after dark, is covered in our guide to bedroom lighting for sleep.
Where to go next
Start with the audit and the free fixes tonight; they take ten minutes. If the window is the problem, decide between curtains, a blind or both, and if the light is coming from a person rather than a window, try a mask before spending on the room.
Darkness is one of three things that make a bedroom work, alongside quiet and a cool temperature. The other Sleep Environment guides cover the rest, and if you are choosing curtains specifically, the blackout curtains buying guide explains linings, fittings and what to look for on the label.
Sources and further reading
- NHS Every Mind Matters: How to fall asleep faster and sleep better
- Journal of Clinical Endocrinology and Metabolism: Gooley JJ et al. Exposure to room light before bedtime suppresses melatonin onset and shortens melatonin duration in humans. Journal of Clinical Endocrinology and Metabolism, 2011
- Sleep Foundation: Sleep Foundation
- The Sleep Charity: The Sleep Charity
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Written and reviewed by the Quiet Mind Sleep editorial team in line with our editorial policy. Spotted an error? Let us know.
