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100% blackout: what it really means.
A standard blackout curtain blocks most of the light but often lets halos slip through at the edges, along the bottom and at the joins. The result is partial darkening that does not suit situations where total darkness is required.
A 100%* blackout rating means the fabric itself lets no photon through.
The situations where 100% makes all the difference:
Daytime sleep: shift workers, night shifts, recovery. A single halo of light is enough to disrupt the circadian cycle and sleep quality.
Baby's room: total darkness helps babies fall asleep and makes naps last longer. Especially effective in summer when evenings stay light until 10pm.
Home cinema: a projection screen loses contrast as soon as any light source remains. Total blackout restores deep blacks.
Remote work and video calls: control natural light to avoid reflections on the screen and backlighting on video calls.
*Under optimal installation and test conditions.
To add thermal insulation (up to 7°C of gain) to total blackout, see the made-to-measure thermal blackout curtain collection.
| Category | Density | Blackout | Thermal gain | Sound attenuation |
|---|---|---|---|---|
| Standard thick curtain | 150 to 300 g/m² | 40 to 70% | 1 to 2°C | 5 to 7 dB |
| Mid-range | 300 to 500 g/m² | 70 to 90% | 2 to 4°C | 12 to 18 dB |
| High performance | 500+ g/m² | 95 to 100% | 5 to 7°C | 18 to 25 dB |
| Kurtens 3-en-1 | 620 g/m² | 100 %* | Up to 7°C* | 22 dB* |
*Data from tests carried out under optimal conditions.
Blackout curtains and thermal curtains are often confused. Our 3-in-1 curtain combines both; our blackout models focus on total darkness.
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A blackout curtain is defined by how much light it blocks, 100%* at Kurtens. Its main function is darkening.
A thermal curtain is defined by its resistance to heat exchange, and its role is insulation against the cold in winter and the heat in summer.
*Under optimal installation and test conditions.
To go further, see our comparison: thermal blackout curtain vs standard blackout curtain.
Why dimensions matter for total blackout.
A 100% blackout curtain can fail to deliver on its promise once installed. The reason is simple: light halos do not come from the fabric but from poorly covered edges.
That is why choosing the right size, or going made-to-measure, is just as important as the fabric itself.
The three points of light leakage in a poorly sized curtain:
- The sides: a 2 cm gap between the curtain and the wall lets in two lines of light visible in the dark
- The bottom: the gap at the floor creates a strip of light that is enough to wake a sleeper
- The top: if the curtain does not rise high enough above the window, light passes over the top
At Kurtens, our standard sizes are calculated to cover the most common French windows with the recommended overlaps. And if your window is unusual, the made-to-measure option lets you enter your exact dimensions with a side overlap of 15 to 20 cm on each side, a 2 to 3 cm pool at the floor and a height that rises sufficiently above the glazing. In both cases, 100% blackout is guaranteed under optimal installation conditions.
How to order your made-to-measure blackout curtain.
Kurtens blackout curtains are made to order at no extra cost and to your exact dimensions. The process is simple and takes less than two minutes.
Choose your color from our 7 shades: Grey, Off-white, Cream, Mint Green, Green, Lilac or Blue. Every color delivers exactly the same blackout, thermal and soundproof performance.
Select your size: 4 standard sizes are available (100x150, 150x230, 250x230, 300x270 cm) or enter your custom dimensions to the exact centimetre. The maximum height is 270 cm, with no width limit. For patio doors or non-standard windows, made-to-measure guarantees full coverage with no light halo.
Choose your heading type to match your existing rod, then confirm your order. Your curtain is made and shipped within 2 to 3 weeks with free delivery in mainland France, Belgium, Switzerland and Luxembourg.
Need help with measurements? See our size guide. For large windows and patio doors, explore our made-to-measure wide-width collection and our made-to-measure patio door curtain collection.
The right blackout curtain depends on how you mainly plan to use it and the type of window you want to cover.
For a living room or a home office, blackout removes glare on screens and lets you control brightness during video calls. If you also want to filter outside noise (busy street, neighbours), our 3-in-1 curtain adds 22 dB of sound attenuation on top of the blackout.
For a home cinema or a screening room, total darkness is essential to render deep blacks on screen. Made-to-measure is especially recommended here, because the slightest light halo compromises the experience.
To go further, read our complete guide to understand the difference between blackout, light-filtering and opaque curtains, or explore our made-to-measure soundproof curtains if sound insulation is your main priority.
For a bedroom or a baby's room, total blackout is the priority. A made-to-measure curtain fitted to your exact dimensions eliminates the light leaks that disrupt sleep. In summer, closed, it blocks direct solar radiation and limits overheating. For a measured thermal gain (up to 7°C), see our made-to-measure thermal blackout curtain.
The ANSES confirms that exposure to artificial light at night disrupts biological rhythms and sleep, and recommends total darkness to let the internal clock synchronise.
For a living room or a home office, blackout removes glare on screens and lets you control brightness during video calls. If you also want to filter outside noise (busy street, neighbours), our 3-in-1 curtain adds 22 dB of sound attenuation on top of the blackout.
For a home cinema or a screening room, total darkness is essential to render deep blacks on screen. Made-to-measure is especially recommended here, because the slightest light halo compromises the experience.
To go further, read our complete guide to understand the difference between blackout, light-filtering and opaque curtains, or explore our made-to-measure soundproof curtains if sound insulation is your main priority.
Frequently asked questions.
What is a 100% blackout curtain?
A 100% blackout curtain is a curtain whose fabric lets no light through*. Unlike partial blackout curtains, which filter 85 to 95% of light, the 100%* version guarantees total darkness whatever the outdoor light intensity.
*Under optimal installation and testing conditions.
What is the difference between a blackout curtain and an opaque curtain?
Opaque means you cannot see through the fabric. Blackout means the fabric lets no light through, even in full sun. A curtain can be opaque without being fully blackout.
Do blackout curtains protect against summer heat?
Yes. Closed during the day facing the sun, a blackout curtain blocks the rays and limits overheating. Our 3-in-1 curtain adds measured thermal and soundproof insulation on top.
Is a blackout curtain suitable for a baby's room?
Yes, it is even one of the most recommended uses. Total darkness helps falling asleep and lengthens naps, especially in summer when the light takes a long time to fade.
Do blackout curtains offer protection against noise?
A standard blackout curtain offers slight sound attenuation through its mass, but that is not its primary function. For true sound insulation, you need a curtain built with a high-density fabric specifically selected for sound absorption. Our 3-in-1 curtain combines both: 100%* blackout and 22 dB* of sound attenuation in a single curtain. For a soundproof priority, see our made-to-measure soundproof curtains.
*Data from tests carried out under optimal conditions.
What is the difference between a blackout curtain and a light-filtering curtain?
A light-filtering curtain filters light without blocking it entirely: it lets through a soft, diffuse light while preserving daytime privacy. A blackout curtain blocks light completely to create total darkness. The choice depends on the use: light-filtering for the living room during the day, blackout for the bedroom, the home cinema, or any room where complete darkness is needed. Read our dedicated article
Is it better to sleep with or without blackout curtains?
Sleep studies (links to the studies: link 1, link 2) show that darkness promotes the production of melatonin, the sleep hormone. Blackout curtains are especially beneficial if you sleep in an environment with light pollution (street lamps, signs), if you work shifts, or for children's rooms in summer when daylight comes very early. A curtain combining blackout and thermal insulation, like those from Kurtens, also keeps a stable temperature suited to sleep.
What size should you choose for a made-to-measure blackout curtain?
Measure the width of your window and add 15 to 20 cm on each side to cover side light leaks. For the height, measure from the rod fixing point down to the floor and add 2 to 3 cm so the curtain just grazes the floor without dragging. If your window exceeds the standard sizes, enter your exact dimensions in our made-to-measure configurator (maximum height: 270 cm).
What is the delivery time for a made-to-measure blackout curtain?
Each made-to-measure curtain is made to order. Allow 5 to 7 days for production and 5 to 10 days for delivery. Delivery is free in mainland France, Belgium, Switzerland and Luxembourg.
Can I order a made-to-measure blackout curtain for a patio door?
Yes. Our made-to-measure curtains cover every width, with a maximum height of 270 cm. For wide patio doors, we recommend ordering two fitted panels that meet in the centre with no light getting through.
Blackout curtain or blackout: what's the difference?
None, fundamentally: blackout is the English term for total light blocking. The difference is one of degree. Many curtains sold as blackout filter 85 to 95% of the light and leave a grey haze. A true blackout blocks 100%* of the light, with no glow. Kurtens blackout curtains are blackout in the strict sense: they block 100%* of the light.
*Under optimal installation and test conditions.
Very blackout curtain: how can I be sure it really blocks 100%?
Two criteria. First the fabric weight and composition: a lightweight curtain or one without a blackout membrane lets a haze of light through. Kurtens weighs 620 g/m² with a blackout membrane, meaning 0 lux transmitted*. Second the dimensions: even a 100%* blackout fabric leaves a sliver of light if the curtain is too tight. Made-to-measure covers the area around the window and removes that glow.
*Under optimal installation and test conditions.
How do I get total darkness with no sliver of light at the edges?
Total darkness depends as much on the fitting as on the fabric. For complete darkness, the curtain must extend past the window on the sides and drop below the sill, so no light can get around it. A made-to-measure blackout curtain, built to the exact dimensions of your window, removes the side and bottom glow that standard sizes leave behind. The 620 g/m² Kurtens fabric blocks 100%* of the light across its entire surface.
*Under optimal installation and test conditions.
