Blackout Blinds: How Dark Can You Really Get a Room?

Blackout blinds use a fabric that stops light passing through it. On their own, though, they rarely make a room completely dark — light sneaks in around the edges. A blackout roller blind mounted outside the recess with a generous overlap gets most rooms dark enough to sleep; adding side channels, a cassette or a blackout curtain in front gets you close to total darkness.

What makes a fabric "blackout"

Blackout fabrics are either coated — a woven fabric with a light-blocking backing, often white or silver — or multi-layer, with an opaque layer woven into the cloth. Hold a sample up to a bright window: a true blackout fabric shows no light at all through the weave.

Dim-out fabrics, by contrast, reduce light heavily but still let a little glow through. They are fine for living rooms, but not for daytime sleep.

Which blinds can be blackout?

• Roller blinds: the best option — flat blackout fabric with nothing to let light through.
• Roman blinds: blackout lining blocks light through the fabric; small leaks at the sides and folds.
• Zebra blinds: blackout bands make them much darker, but the sheer bands still pass some light.
• Honeycomb blinds: blackout cells plus insulation — excellent for hot bedrooms.
• Vertical blinds: blackout louvres help, but light passes between them.
• Venetian and wooden blinds: not blackout; light passes between slats and through cord holes.

Where the light gets in

1. At the sides, especially with inside-mounted blinds that need a small clearance.
2. At the top, around the roll and brackets.
3. At the bottom, if the bottom bar doesn't sit against the sill.
4. In the middle, where two blinds meet on a wide window.

How to stop the leaks

• Mount outside the recess with about 3 to 4 inches of overlap on each side and above the opening.
• Use a cassette to cover the roll and close the gap at the top.
• Add side channels — slim profiles that hold the fabric edges so light can't pass.
• Let the bottom bar rest on the sill for inside mounts, or overlap below it for outside mounts.
• Use one blind instead of two side by side where the width allows, or overlap them.
• Add a blackout curtain on a ceiling-mounted track in front of the blind.

Our measuring guide explains how to size an outside mount.

Who needs blackout blinds?

• Anyone who sleeps during the day — shift workers, new parents, students.
• Babies' and children's rooms, for naps and early summer sunrises.
• Home theatres and media rooms.
• East-facing bedrooms, where summer sunrise light arrives very early.
• Hotels and guest rooms.

A bonus: heat control

Blackout fabrics with a white or reflective backing bounce sunlight back out through the glass, which keeps west- and south-facing rooms noticeably cooler in summer and eases the load on air conditioners.

Colour choices

Because the backing faces the window, you can choose almost any colour for the room side. Deeper colours feel cosy in bedrooms; light colours keep the room bright when the blind is open.

What blackout blinds cost

Blackout fabrics cost a little more than standard ones, but they still fall within our ₹130 to ₹350 per sq ft range, including installation. A 5 × 5 ft bedroom window (25 sq ft) costs about ₹3,250 to ₹8,750; side channels are usually an extra item. See our guides to roller blinds and the best blinds for bedrooms.

Want exact numbers for your windows? Book a free site visit anywhere in Delhi NCR — we measure every window and give an itemised quote within the ₹130 to ₹350 per sq ft range, installation included. Browse our window blinds collection to shortlist styles first.

Frequently asked questions

Do blackout blinds block 100% of light?

The fabric itself blocks light completely, but light can still enter around the edges. Outside mounting, a cassette, side channels or a curtain in front can bring the room close to total darkness.

Should blackout blinds be mounted inside or outside the recess?

Outside, if darkness is the priority. An outside mount overlaps the opening on all sides, which blocks far more light than an inside mount with its small side gaps.

Do blackout blinds reduce heat?

Yes. Blackout fabrics with a white or reflective backing reflect sunlight back out, reducing heat gain through the glass — especially on west-facing windows.

Are blackout blinds good for kids' rooms?

Very. They help children nap during the day and sleep through early summer sunrises. Choose a cordless, chain-tensioned or motorised mechanism for safety.