How dark should your bedroom be?

Here's a quick way to tell whether light is getting into your bedroom. Turn off every light tonight, get into bed and give your eyes a few minutes to adjust. Then hold your hand up in front of your face. If you can see it, light is getting in from somewhere. The places to look first are the edges of the curtains, the gap under the door and the standby lights on anything that's plugged in.

It's worth finding them, because closing your eyes cuts out most of the light, but not all of it ². A streetlight coming in around the curtains still gets to your eyes after you've shut them. While you sleep, you want the room as dark as you can make it ¹.

Most of what you find, you can fix with things you already have in the house. The window takes longer, but a mask may be all you need.

The small lights around the room

Start with anything that glows. The standby lights on the TV, a charger, a power strip or the router are tiny, but you'll notice every one of them once the room is dark. A strip of dark tape over each one takes care of it. A clock with a bright display can face the wall, or you can turn it down to its dimmest setting. And a phone that lights up with every message can go face down on the nightstand, or out of the bedroom altogether.

Light from a hallway or bathroom comes in under the door. When someone in the house goes to bed later than you, that light can stay on for a while after you've turned in. A rolled towel or a draft stopper along the bottom of the door blocks it.

When the light comes in the window

The window is the hardest leak to fix, whether it's a streetlight, a neighbor's security light or the sun coming up on a summer morning well before your alarm. Curtains only work if they cover the whole window, because light gets in around the sides and over the top. New ones should be wider than the window frame and long enough to hang below the sill. Where the two curtains meet in the middle, a clothespin or a binder clip will hold them shut. In a hotel, a clip hanger from the closet does the same job.

If you rent, you can leave the landlord's blinds where they are. A blackout curtain on a tension rod fits inside the window frame, and it doesn't need any drilling. Removable blackout film goes straight onto the glass, and it peels off when you move out.

A window that looks fine at midnight can let in plenty of light on a June morning, long before you mean to be up, so check the room again once summer comes.

Should you get blackout curtains or an eye mask?

Try a mask first, because it's cheap and it works in any room. A mask that fits well blocks light from every direction, and it comes with you when you travel. Curtains are worth it when you can't get used to something on your face, or when the window is so bright that you'd rather fix it once for everyone in the room.

After a week of sleeping in an eye mask, young adults did a little better on a memory test and a reaction-time test than after a week with nothing over their eyes ³. That was in summer, with their curtains open, and they didn't feel any more alert ³.

Get one with an adjustable strap, so it stays put when you roll over, and a shape that sits off your eyelids. Light coming in at the bridge of your nose means it needs tightening or a different shape.

A mask is also the easiest answer when you share the room. Your partner might read after you've turned in, or fall asleep with the TV on, and a mask works no matter what they're doing. Wear one tonight, and sort out the lamp with them tomorrow, when you're both awake.

What to do about dark mornings

Blackout curtains keep out the morning light too, and that's light you want. Once you've hung them, I'd make a point of getting outside early in the day. Open the curtains on your way out of the bedroom, so the room isn't dark all morning.

The curtains can also leave the room dark when your alarm goes off. A sunrise alarm clock gets around that. It starts lighting up the room before the alarm sounds, so you don't wake up in the dark.

What kind of night-light to use

You still need to see the floor when you get up for the bathroom at night. A little light for that is fine, as long as the room goes dark again once you're back in bed ¹. Use the dimmest light that gets you there, plugged in low along the path from the bed to the door, so it lights the floor and stays out of your eyes.

Go for a red or amber one over white. Those colors do less to your body clock than white or blue light of the same brightness ¹. In a hallway or bathroom, a motion-sensor night-light comes on only when you're up and turns itself off again, so nothing is glowing under the door while you sleep.