How do you choose blackout curtains for a bedroom that stay dark?

Updated October 7, 2026.

A bedroom that glows before dawn has a hardware problem rather than a willpower problem, and the remedy is mostly geometry. Blackout is a claim about cloth, and a room is not a swatch. Sleep responds to the whole room, and to the hardware that holds the cloth against the wall.

Short answer: Buy a panel with a true multi-layer or coated blackout core, then spend the rest of your effort on the gaps around it. Mount the rod 4 to 6 inches above the frame, and run it 6 to 12 inches past each side. Buy panels totalling 2 to 2.5 times the rod width, so they overlap in the middle. One laboratory night at 100 lux raised nighttime heart rate and next-morning insulin resistance in young adults.

This guide is for: anyone whose bedroom faces a streetlight, an early sunrise, or a work schedule that means bedtime while it is still light outside.

Key Takeaways

1. One night under 100 lux raised nighttime heart rate and next-morning insulin resistance in 20 young adults, against a night under 3 lux (Healio, 2022).
2. The most light-sensitive person in one study lost half their melatonin at about 10 lux, while the least sensitive needed 400 lux (PMC, 2022).
3. Of 14 seller pages we read in September 2026, 6 stated a percentage, 6 used words with no number, and 2 gave lux estimates instead.

On This Page

Why does a dark bedroom matter for sleep?

One night at 100 lux raised heart rate and morning insulin resistance. The most light-sensitive people react at just 10 lux.

The dose of light that changes the body overnight is considerably smaller than most people picture as darkness. In a Northwestern laboratory study, 20 young adults slept two nights under set lighting (PNAS via PMC, 2022). One group had a night under 3 lux, then a night under ordinary room light at 100 lux. That single lit night raised nighttime heart rate and next-morning insulin resistance (Healio, 2022). The room never looked bright. That distance between what a bedroom looks like and what the body registers overnight is the entire reason to close the edges.

Evening light works on an even lower threshold. In one dose-response study, the most sensitive person lost half their melatonin at about 10 lux, which a review of the study compares to dim reading light (PMC, 2022). The least sensitive person needed 400 lux, and that spread is why one housemate sleeps through a streetlight and the other does not. Sleep researchers often treat 10 lux as the line between dim and brighter rooms (PMC, 2021). Even at 1 lux all night, 33 volunteers showed no drop in melatonin metabolites, yet their sleep still broke up more often (IJERPH, 2020).

What does a blackout label promise about darkness?

The rating describes a swatch on a test rig, not your room. Treat the published percentage as a ceiling and plan for the gaps.

Darker mornings start with reading the rating as a ceiling rather than a promise. The published percentage rates a swatch of cloth on a test rig, and it says nothing about the bedroom that panel will eventually hang in. Sellers' own guides disagree with each other, and the disagreement is the useful part. One guide puts true blackout at 90 to 100 percent and room darkening at 70 to 85 percent (uscurtains). Another sets room darkening at 80 to 95 percent, and warns that a faint glow can remain at the edges (Homerilla). A third splits the two again, with blackout at 100 percent and room darkening at about 90 to 95 percent (Moondream). Three yardsticks are in play. None was applied in a real bedroom.

Assume the finished window will perform worse than the test figure, because the rating covers the cloth alone. Light still enters at the top, sides and bottom (Allure Window Treatments, 2026). The shopping list then reorders itself, away from the last percentage of fabric density and towards width, height and hardware. In our judgement, a mid-range panel hung high and wide beats the densest panel hung inside the frame.

Where does light still get in after the curtains close?

Light arrives around the panel, not through it: the top gap, the side gaps, the center split and the floor gap, in that order.

The cloth is rarely the failure point. Light travels around a panel as easily as through it, and a standard rod leaves four open paths before the weave matters. The table below is our own ranking for a typical bedroom window, and it rests on judgement rather than measurement, because this publication owns no instruments.

Working down that order spends the cheapest money first, since a wider rod costs less than a better panel and closes two paths at once. Test the last row before buying anything, by holding the cloth against a strong light. A halo through the weave means it is not a true blackout. A technical multi-layer panel lets nothing through, even with a flashlight pressed against it (Kurtens, 2026). If the cloth passes that test and the room still glows, the light is coming around the panel, and the next section covers how to close those paths.

How should blackout curtains be hung so they work?

Mount high, run the rod 6 to 12 inches past each side, buy 2 to 2.5 times the rod width in fabric, and close the center overlap.

Trade guidance and energy-saving advice point the same way, so the installation recipe you need is short. Set the rod at least 4 to 6 inches above the frame, and extend it 6 to 12 inches past the frame on each side. Then buy total fabric width of 2 to 2.5 times the rod width (Curtarra, 2025). Width buys the overlap, and the overlap closes the center seam.

The sealing steps come from energy advice written for heat, and they work just as well for light. Hang the curtains as close to the window as possible, and install a cornice at the top. Then seal the panels at the sides, and overlap them in the middle (Consumer Reports, 2023). The same guidance names hook-and-loop tape or plain tape for that sealing and overlapping work. That advice was written for heat. It works as well for light.

Allow extra rod at each end for bulk. Large grommets, thick blackout lining and deep pinch pleats all make a wider stack when the panel is open (Homestyle Calculator, 2026). A hem touching the floor closes the fourth path, and a track fixed to the ceiling closes the first one. Generous hardware makes the same fabric perform better.

Which is better for a bedroom, blackout curtains or blackout shades?

Shades sit closer to the glass and lose less light at the sides; curtains cover more wall. Many bedrooms need both, layered.

The two products fail in different places, so the right answer depends on your particular window. A shade mounted inside the frame sits within an inch of the glass. Shades work best when drawn all day and mounted as close to the glass as possible, which creates a sealed space (Consumer Reports, 2023). Their weakness is the narrow channel at each edge, because the shade always runs narrower than the recess it sits in.

Blinds are the weakest for sleep. Slats tilted shut still leave a line of light at every joint, and the cord opening adds one more.

Curtains cover wall as well as glass, and hung near the ceiling they beat a shade at the top edge, which is the leak most people notice first. Layering is the usual answer for a bright bedroom: a shade inside the frame for the glass, and a wide panel outside it for the surrounding wall. Retailers sell the same pairing as a styling choice, putting sheer curtains with blackout panels so a room can switch between daylight and privacy (IKEA curtains). It happens to close two leak paths at once.

What do the product pages say side by side?

We read 14 seller pages in September 2026 and sorted them into three buckets: percentage claims, word claims and lux estimates.

We read 14 retailer and manufacturer pages about bedroom blackout curtains on 20 and 21 September 2026. We counted only what each page states about blocking light, and we measured nothing here; the counting is the entire contribution, and our method page describes how it works.

Bucket A is the only one you can compare across shops, because a stated band gives a yardstick to hold the next page up to, even though the rig was never a bedroom. One guide puts true blackout at 90 to 100 percent (uscurtains), and another sets room darkening at 80 to 95 percent (Homerilla). Read both as ceilings, and buy the extra width neither page mentions.

Bucket B was entirely IKEA, whose pages avoid numbers in both directions. The KORGMOTT page says the fabric blocks out all light and glare on screens (IKEA KORGMOTT), while the VILBORG page says the room-darkening fabric lets in a small amount of light (IKEA VILBORG). Bucket C's two pages state that their lux figures are converted from maker-reported blocking percentages rather than measured (UBlockout, 2026). Know that before treating any lux claim as evidence.

Do blackout curtains make a bedroom cooler or quieter?

Some drapes cut summer heat gain by about a third when closed on a sunny window. On noise they do far less than the marketing implies.

The thermal case is genuine and modest. Studies have found that medium-colored draperies with white plastic backings can reduce heat gain by 33 percent. The ability of curtains to do that depends on fabric type and color (Consumer Reports, 2023). A blackout panel is heavier and more thoroughly lined than a plain one, so closing it on a sunny window before the sun reaches the glass should keep the bedroom cooler by bedtime.

Noise is where the marketing outruns the physics. Fabric soaks up sound bouncing around inside a room. Stopping sound from entering takes mass and a sealed edge, which a hanging curtain does not have. An acoustics supplier states the realistic figure plainly: even the heaviest curtains with a near-airtight seal let most sound through, and 1 to 5 decibels of reduction is the range to expect (Second Skin Audio, 2025).

If traffic or a neighbour wakes you, the curtain is the wrong tool, and masking sound is the cheaper one. Our guide on white noise for sleep covers how to set that up. Buy the panel for darkness and warmth, and treat any reduction in noise as a bonus.

What should you check on the label before you buy?

Price buys width, lining layers and hardware rather than darkness. The cheapest panel with a wraparound rod can beat a costly one.

Start with construction. A light-colored single-layer panel at 200 g/m² will never block all light. A multi-layer panel at 500 g/m² or more blocks it in any color (Kurtens, 2026). Weight and layer count say considerably more than the color swatch does. Woven and coated blackout behave differently in the wash, and one retailer's tell is worth borrowing: a panel warning "do not fold sharply" or "coating may transfer" is a foam-backed cloth (Homerilla).

Certifications answer a different question than darkness does. OEKO-TEX Standard 100 covers whether the fabric was made without harmful substances (Moondream), and it says nothing about how much light a panel stops.

Spend on width and hardware before spending on the panel. Ready-made prices spread widely at one retailer, where the cheapest blackout option ran about $20 for two panels and a pricier pair about $75 (House Digest, 2024). In our judgement, two cheap pairs on a wide, high rod, overlapped in the middle, beat one costly pair, and a rod that stops at the frame wastes whatever you paid for the cloth.

Common questions

Do blackout curtains block 100 percent of light?

No. Blackout fabric blocks 99 to 100 percent of light through the cloth, but that figure covers the fabric only. Light still gets in through gaps at the top, sides and bottom (Allure Window Treatments, 2026). Fix the gaps first. A wider, higher rod closes most of them.

Will a blackout curtain keep the bedroom cooler in summer?

Usually yes, provided it closes before the sun reaches the glass. Consumer Reports advises keeping curtains closed on summer days, particularly on the side of the home where the sun is coming in (Consumer Reports, 2023). Close it after your room is already hot, and the heat stays trapped inside.

Are blackout curtains worth it in a child's room?

Children look at least as light-sensitive as adults. In preschool-aged children, melatonin fell an average of 78 percent in response to light measured at 5 to 40 lux. In most of them it had not rebounded 50 minutes after the light went off (University of Colorado Boulder, 2022). In a child's room, choose cordless hardware as well, because loose cords are a strangulation risk for young children.

Can I add blackout to curtains I already like?

Yes, and a separate lining is often the cheaper route, since a blackout liner behind an existing panel adds layers and mass. Then seal the sides and overlap the panels in the middle, with a cornice at the top (Consumer Reports, 2023). Widen your rod at the same time, because the extra bulk needs somewhere to stack.

Does street lighting outside really affect sleep?

Small amounts of light still register. In one experiment, 33 volunteers slept a whole night under 1 lux, and their sleep was more fragmented, although melatonin metabolites did not fall (IJERPH, 2020). A streetlight through a gap is brighter than that, so close the gaps rather than shopping for denser cloth.

How do I wash a blackout curtain without ruining it?

Follow the panel's own label, since woven and coated panels differ. IKEA's ROSENMANDEL page states maximum 4 percent shrinkage and cold machine wash on a normal cycle. The same page rules out tumble drying, and allows steam ironing on the front side only (IKEA ROSENMANDEL). Coated panels are the ones that crack and shed when folded hard.