Blockout Curtains vs Blockout Blinds — Which Actually Blocks More Light?
The short answer: “Blockout” (the same thing as “blackout”) means an opaque, usually foam-coated fabric that stops light passing through the cloth itself. Both curtains and blinds come in blockout versions, but they fail in different places. A blockout blind blocks light through its panel, yet leaves visible gaps down the sides, across the top where the roller sits and along the bottom, because it mounts inside or just outside the window recess. A blockout curtain can be hung wide and long so it overlaps the wall around the window and covers those edges — which is why, fitted properly with a good fabric, curtains usually win on true darkness. Blinds are neater and take less space; curtains give the deeper blackout and add useful insulation. For a bedroom or nursery where you want genuine dark, blockout curtains, or a blind and curtains layered together, are the stronger choice.
People shopping for a dark bedroom often assume “blockout” is a single setting you either have or you don’t. It isn’t. Blockout describes the fabric, and how dark a room actually goes depends far more on how the covering is mounted than on the label on the cloth. That is the whole difference between a blockout curtain and a blockout blind.
First, what “blockout” actually means
Blockout fabric is an opaque, foam-backed cloth designed to stop light. It is made by coating a fabric in layers, or “passes”: a two-pass blockout applies a black foam layer and then a lighter one, while a three-pass adds white foam first, then black, then a finished layer, so it can work as both a decorative face fabric and a blackout lining. Tightly woven fibres and that opaque coating together form the barrier. It blocks the great majority of light through the panel, though a lighter blend can still let a little filter through — “blockout” is not automatically one hundred per cent.
Where each one leaks light
This is where curtains and blinds part ways. A roller-style blockout blind sits inside or just outside the window recess, so however opaque the panel is, light spills in along both side edges, across the top where the roller housing sits, and along the bottom. Side channels and a cassette top help, but the mounting itself always leaves seams for light to find. A curtain has no such constraint: hung on a track wider and longer than the window, it overlaps the wall on every side and puddles past the sill, covering the exact edges where a blind leaks.
Which blocks more light
For genuine, sleep-quality darkness, a well-fitted blockout curtain in good fabric beats a standard blockout blind, simply because it can seal the perimeter the blind cannot. The blind’s advantage is neatness and space, not darkness. If you want the best of both — the tidy look and near-total dark — the answer is to layer them: a blackout blind inside the recess with blockout curtains drawn over the top.
Beyond darkness: warmth and noise
Blockout fabric earns its keep in two other ways. Its density and layered construction add thermal insulation, helping hold a room’s temperature by trapping an extra air layer — useful against both summer heat and winter cold. The same heavy cloth also absorbs some sound, taking the edge off outside noise, though no curtain is truly soundproof. Among blinds, cellular (honeycomb) blinds insulate especially well; a plain roller blind does less.
| Blockout curtains | Blockout blinds | |
|---|---|---|
| Light through the panel | Opaque | Opaque |
| Light leak at edges | Covered by overlapping the wall | Gaps at sides, top and bottom |
| Best-case darkness | Near-total, fitted correctly | Partial unless in side channels |
| Insulation | Good — adds an air layer | Excellent (cellular), less (roller) |
| Look & space | Soft, uses wall space | Neat, minimal, close to glass |
| Best for | Bedrooms, nurseries, media rooms | Small windows, tidy modern look |
So which should you choose?
Choose a blockout blind when the priority is a clean, compact look and the room only needs to be dimmed rather than pitch dark. Choose blockout curtains when real darkness matters — a bedroom you sleep late in, a nursery, or a media room — because a curtain can seal the light gaps a blind leaves. And when nothing but total dark will do, use both.
Frequently asked questions
What is the difference between blockout and blackout?
None — they are two spellings for the same thing: an opaque, light-blocking fabric. “Blockout” is the more common term in South Africa and Australia, “blackout” in the UK and US.
Do blockout curtains block 100% of light?
The fabric blocks most light, and some lighter blends let a little through. Hung wide and long so they overlap the window on every side, blockout curtains get very close to complete darkness.
Do blockout blinds block all the light?
No. Because they sit in or just outside the window recess, they leave gaps at the sides, top and bottom. Side channels and a cassette reduce the leaks but do not fully seal them.
Which is better for a nursery or a dark bedroom?
Blockout curtains, or a blackout blind and blockout curtains layered together, give the most complete darkness because the curtain covers the edges a blind cannot.
Do blockout curtains keep heat in?
Yes. The dense, layered fabric adds an insulating air layer that helps hold room temperature, and it absorbs some noise too — though it is not soundproof.
Can I get total darkness from a blind alone?
The closest a blind gets is a blackout blind fitted in side channels or a cassette. For genuine full darkness, pair it with blockout curtains.
Are blockout curtains and thermal curtains the same?
They overlap but are not identical. Blockout fabric’s density gives a thermal benefit, but you can also have a thermal lining that is not fully blackout, or blackout that is chosen mainly for darkness.