100% Blackout Curtains: How to Get Total Darkness
A true 100% blackout curtain blocks all light, but total darkness depends as much on the fabric as on how it is hung. Most curtains sold as “blackout” block direct light without reaching complete darkness, because light leaks in from the sides, the top and the bottom.
This guide explains what sets a true 100% blackout apart from an ordinary blackout, how to decode the levels of blackout, and how to achieve complete darkness in a room.
Why a “blackout” curtain often still lets light through
A curtain labelled “blackout” is not necessarily a 100% blackout. Many block direct light but leave a residual halo, for two reasons.
First the fabric: too thin, too loosely woven or without a dense layer, it lets daylight filter through. Second, and this is the most common, the leaks at the edges. Light gets around the curtain at the sides, over the top above the rod, and at the bottom if the curtain stops too short. A 100% blackout fabric hung badly leaves a room far from complete darkness. The full diagnosis of light leaks is in our article on light coming in at the sides of the curtain.
What makes a true 100% blackout
A true 100% blackout comes down to fabric construction, not colour. There are two approaches: a dense layer applied to the back of the fabric, or a core of tightly packed yarns set between the layers that absorbs light. The best-performing curtains combine a tight weave with a technical layer on the back.
Colour does not determine blackout: a light fabric built correctly blocks as much as a dark one. We cover this in detail in our article on the white blackout curtain. For complete darkness, Kurtens offers a certified 100% blackout, in several colours and fabrics.
Decoding the levels of blackout
Not all curtains that “darken” are equal. Here is how to place what you are buying.
| Type | Effect on light | Use |
|---|---|---|
| Sheer / light-filtering | filters daylight, keeps the brightness | daytime privacy |
| Semi-blackout | darkens heavily, residual halo | living room, living space |
| Standard blackout | blocks direct light, possible leaks at the edges | bedroom |
| 100% blackout | complete darkness if zero leaks | baby's room, daytime sleep, projection |
The term “blackout” covers everything except sheers: on its own, it does not guarantee 100%. For the difference between blackout, light-filtering and opaque, see our comparison of blackout, light-filtering and opaque.
Kurtens covers these levels made-to-measure, from semi-blackout to 100% blackout, in several fabrics, colours and styles, to match the blackout to each room.
Achieving complete darkness: fabric is not enough
A 100% blackout fabric only delivers complete darkness with no light leaks. Three rules:
- Cover wide: the rod extends 15 to 20 cm beyond each side of the window, and the curtain reaches the floor.
- Mount high: fit the rod about 15 cm above the window, or hang from floor to ceiling to remove the halo at the top.
- Go made-to-measure: a curtain cut to the exact size of your wall removes the side gaps that standard sizes always leave.
Simple test: close the curtain in broad daylight and look for a halo around the edges. If there is one, the problem almost always comes from the fit or the dimensions, not the fabric.
Which rooms 100% changes everything for
100% blackout is not just a comfort. In some rooms, it changes your quality of life.
- Bedroom: darkness helps you fall asleep and sleep deeply, especially in summer when daylight comes early.
- Baby's or child's room: daytime naps and early bedtimes call for complete darkness.
- Night work: sleeping during the day requires total blackout, impossible with a partial blackout.
- Home cinema: a dark room matters more than an expensive projector, as we explain for the home cinema curtain.
Frequently asked questions
Does a blackout curtain block 100% of the light?
Not always. “Blackout” does not mean 100%. The result depends on the fabric construction and the fit: an ordinary blackout blocks direct light but often leaves a halo.
Why does my blackout curtain let light through?
Most often because of leaks at the edges: the sides, the top above the rod, a bottom that stops too short. It is a problem of dimensions and fit before it is a problem of fabric.
Does a curtain's colour change the blackout?
No. It is the fabric construction that blocks light, not the shade. A light fabric designed correctly blacks out as much as a dark one.
How do you achieve complete darkness in a bedroom?
A 100% blackout fabric, hung wide and high (15 to 20 cm of overhang, floor to ceiling if possible), preferably made-to-measure to remove the side gaps.
What is the difference between blackout and 100% blackout?
A blackout blocks direct light. A 100% blackout delivers complete darkness, provided every leak is eliminated. The difference comes down to the fabric and the fit.
Does made-to-measure improve the blackout?
Yes. A curtain cut to the exact size of your wall removes the side gaps that standard sizes always leave, the leading cause of a halo.
For the right level of blackout at your dimensions, explore Kurtens made-to-measure blackout curtains, from semi-blackout to 100% blackout, in several fabrics and colours, made to the exact centimetre.
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