How Dark Should Your Bedroom Be for Good Sleep?
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How dark should your bedroom be? For most adults, as dark as you can comfortably make it: dark enough that you can't read by it, with no lights shining on your face. This guide covers what the research says about light during sleep, what "dark enough" looks like in practice, the common light leaks in Australian bedrooms, how to fix them, and when a little light is the safer choice.
The short answer: aim for a bedroom that is close to fully dark while you sleep. In one lab study, sleeping with ordinary overhead room light on (about 100 lux) instead of near-darkness (under 3 lux) raised heart rate overnight, reduced deep and REM sleep and made the body less sensitive to insulin the next morning. Blackout curtains, an eye mask and covering small standby lights get most people there. If you need to get up at night, a very dim light low to the floor is a sensible compromise.
Why darkness matters for sleep
Your body clock uses light as its main signal. The Sleep Health Foundation explains that when your eyes sense light, they send signals to the master clock in the brain, and that light is the most important external signal for the biological clock (source). For more on how this works, see body clock and circadian rhythm explained.
Light also affects melatonin, the hormone that rises in the evening. One study compared ordinary room light (under 200 lux) with dim light (under 3 lux). Room light before bedtime delayed the rise of melatonin in almost every participant and shortened its duration by about 90 minutes. Room light during the usual sleep hours suppressed melatonin by more than 50% in most trials (source).
What the research found about sleeping with the light on
A 2022 study had 20 healthy young adults sleep in a lab. One group slept a night in dim light (under 3 lux) followed by a night with the overhead lights on (100 lux). The other group slept both nights in dim light (source).
| Measure | Dim light night | Room light night |
|---|---|---|
| Heart rate during sleep | Lower | Higher |
| Deep (slow-wave) and REM sleep | More | Less, with more light stage 2 sleep |
| Insulin resistance next morning | Fell about 4% (comparison group) | Rose about 15% |
The authors concluded that avoiding light during sleep may be beneficial for cardiometabolic health. It was one night in a small group, so it doesn't prove long-term harm, but it's a good reason to turn off the TV and the overhead light.
How dark is dark enough?
There's no official lux target for a home bedroom, but the research gives a useful guide. The "dim" condition in these studies was under 3 lux, which is very dark. Some practical tests:
- The hand test. Once your eyes adjust, you should barely be able to make out your hand in front of your face.
- No light on your face. Streetlights through a gap, a charger LED or a hallway light under the door shouldn't land on your eyes.
- You can't read by it. If there's enough light to read a page, it's brighter than it needs to be.
The Better Health Channel's advice is simple: ensure the room is dark enough, and an eye mask may help if you're a shift worker sleeping during the day (source).
Common light leaks, and how to fix them
| Light source | Fix |
|---|---|
| Early summer sunrise | Blackout curtains or blockout blinds; a pelmet or side return stops light spilling round the edges |
| Streetlights and security lights | Blockout lining behind existing curtains; close gaps with a curtain clip |
| Standby lights and chargers | Cover with tape or a small sticker, or move them out of sight |
| Phone lighting up | Face down, on Do Not Disturb, or out of the bedroom. See alarm clock without phone |
| Bright clock display | Turn it away or dim it. The Sleep Health Foundation also suggests covering clocks so you're not watching the time (source) |
| Hallway or bathroom light | Draught stopper or rolled towel under the door |
| A partner reading late | A clip-on book light, or an eye mask for you |
If you can't control the room, such as in a hotel, a share house or on a day-sleep after a night shift, an eye mask is the quickest fix. See do sleep masks work and how to sleep after a night shift.
When some light is the better choice
Total darkness isn't always the right answer.
- Getting up at night. If you get up to go to the toilet, a very dim night light placed low, or a motion-sensor light in the hallway, means you aren't fumbling in the dark. See waking up to pee at night.
- Children afraid of the dark. A dim, warm night light can help a child settle. See kids afraid of the dark.
- Waking up. Darkness at night pairs well with light in the morning. Once you're up, open the curtains or step outside. The Sleep Health Foundation notes that morning daylight is especially useful for your body clock (source).
A blackout room can make it harder to wake naturally, because there's no daylight cue. That's where a reliable alarm comes in.
Where the Sovune Nudge fits
We make the Sovune Nudge, a vibrating alarm wristband, so we're not neutral. In a properly dark room, a glowing alarm clock or lit-up phone is often the last light left, and the Nudge doesn't add one.
- No light in the room, except a small display that lights only when you press the button.
- Shows the time when you press the button, so you can check it without a glowing clock face or unlocking your phone.
- No sound. It wakes you with vibration on your wrist, starting as a gentle tap and building through three intensity levels.
- Each alarm vibrates for a full minute, stepping up as it goes, which helps when blackout curtains mean there's no morning light to wake you.
It comes with a 30-day money-back guarantee.
Quick answers
Should your bedroom be completely dark? As close as you comfortably can. Research suggests light during sleep can affect sleep depth and heart rate, so darker is generally better.
Is it bad to sleep with a night light? A very dim light placed low and away from your face is a reasonable compromise if you need to get up at night or a child needs reassurance.
Is sleeping with the TV on bad? It adds both light and sound to the room. Use a sleep timer or turn it off before you sleep.
Do blackout curtains help you sleep? They can, especially in summer when sunrise is early or if you sleep during the day. Pair them with a reliable alarm so you still wake on time.
For every type of silent alarm compared, see our complete guide to vibrating alarms in Australia.