Quick Answer: What Is a Blackout Curtain?
A blackout curtain is a curtain made with, or lined with, a densely woven or coated fabric specifically designed to block light from passing through, typically eliminating 85% to 99% of incoming light depending on the fabric grade. Beyond darkness, blackout curtains also provide meaningful thermal insulation, helping keep a room warmer in winter and cooler in summer, and add extra sound dampening compared to standard curtains.
Is It Blockout or Blackout?
Both terms describe the same type of light-blocking curtain, with “blackout” being the standard term in the UK and “blockout” used more commonly in some other English-speaking markets such as Australia. You may also see “room darkening” or “dimout” used, though these technically describe a lighter grade of light-blocking fabric, discussed below, rather than being exact synonyms for blackout.
Blackout vs Room Darkening vs Dimout: What Is the Difference?
| Term | Typical Light Blocked | Effect |
|---|---|---|
| Dimout/room darkening | 70% to 90% | Noticeably dims the room but a soft glow remains visible through the fabric |
| Standard blackout | 85% to 95% | Substantially dark, minor light glow possible depending on colour and backlighting |
| Ultra/100% blackout | Up to 99% | Near total fabric darkness, typically achieved with a triple-woven or foam-backed construction |
These percentages describe light blocked through the fabric itself. Even a genuine ultra blackout curtain cannot fully darken a room on its own, since light will still find its way in around the edges, top, and bottom of the curtain regardless of how effective the fabric is.
Are Blackout Curtains a Good Idea?
For most bedrooms, nurseries, and media rooms, blackout curtains are genuinely worth having, offering better sleep conditions, improved privacy, and useful thermal and sound benefits alongside the light control. The main trade-off is that fabric alone, however good the blackout rating, cannot fully replicate the total darkness of a properly fitted blind sitting flush to the window recess, since curtains inherently leave gaps at the sides, top, and bottom. Whether that matters depends on how sensitive you or your household are to residual light.
Ultra Blackout Curtains Explained
Ultra blackout, sometimes marketed as 100% blackout, uses a more advanced fabric construction than standard blackout, typically a triple-pass coating or a dense foam-backed layer, pushing light blocking up to around 99%. This tier costs more than standard blackout but is worth considering for shift workers, very light-sensitive sleepers, or rooms with significant natural light such as an east-facing bedroom catching full morning sun.
Blackout Curtains for the Bedroom
Bedrooms are the most common use case for blackout curtains, and pairing them with a track or pole that sits close to the wall, along with adequate return depth, meaningfully reduces the side light leakage that undermines an otherwise good blackout fabric. Pencil pleat curtains on a track generally seal better at the top than eyelet curtains on a pole, worth considering if total darkness is a genuine priority rather than a nice-to-have.
Blackout Curtains for the Nursery
Many parents choose blackout curtains for a nursery to support more consistent daytime naps and earlier bedtimes during lighter months, since babies and young children are often more sensitive to light-driven sleep disruption than adults. It is worth setting realistic expectations: curtains alone, even a genuine ultra blackout grade, will typically still leave some light bleeding in around the edges. For nurseries specifically, some parents find a well-fitted blackout blind or shade, sitting flush within the window recess, achieves more complete darkness than curtains alone, and pairing a blackout blind with dress curtains for the room’s overall look is a common compromise.
Blackout Curtains for the Living Room
In living rooms, blackout curtains suit media rooms or home cinema setups particularly well, where screen glare is a genuine concern, alongside the general thermal and privacy benefits any room gains from a good blackout lining. Outside of these specific use cases, many households choose thermal rather than full blackout curtains for a living room, prioritising warmth and drape over total darkness during the day.
Choosing Blackout Curtain Colours and Fabrics
| Colour/Fabric | Best For |
|---|---|
| White or cream | Light, airy look while still blocking light via the lining rather than the visible colour |
| Grey or beige | Versatile neutral, works with most existing decor |
| Velvet blackout | Premium look and extra sound dampening, popular for living rooms and formal bedrooms |
| Linen-look blackout | Softer, more textured appearance while retaining full blackout performance via the lining |
| Black or navy | Bold, modern look, though not inherently darker performing than a lighter colour with the same lining grade |
It is a common misconception that curtain colour determines blackout performance. In most cases, the blocking power comes from the lining behind the visible fabric, not the face colour itself, so a soft cream blackout curtain can perform just as well as a black one with the same lining grade.
Maximising Darkness: Fixing the Gap Problem
Since fabric performance alone rarely achieves complete darkness, addressing the gaps around a blackout curtain matters just as much as the fabric grade itself.
- Fit the pole or track wider than the window, roughly 15cm to 20cm beyond each side, so curtains can close with enough overlap to cover the frame fully
- Choose a heading and hardware combination with good return depth, sealing more closely against the wall, covered in our curtain types and styles guide
- Add a pelmet or valance along the top to block light seeping over the curtain rail
- Consider a room-darkening curtain pole or track, designed specifically to minimise the gap between the hardware and the wall
What Are Alternatives to Blackout Curtains?
Blackout roller blinds, fitted flush within the window recess, generally achieve more complete darkness than curtains alone, since there is no fabric edge gap once properly fitted. Blackout Roman blinds offer a softer, more decorative look but can allow some light through the fold gaps. Shutters provide excellent light control and durability, though at a higher cost than either blinds or curtains. Many households combine a blackout blind for genuine darkness with dress curtains for warmth and finished appearance, getting the benefit of both.
Blackout Curtains vs Blackout Lining: Which Do You Need?
If you are buying new curtains, ready-made blackout curtains are the simplest option, with the lining already built in. If you already own curtains you are happy with, adding blackout lining separately is usually more cost-effective than replacing the whole curtain. Our curtain linings guide covers lining types, cost, and how to add lining to existing curtains in full detail.
Blackout Curtains Cost Breakdown
| Item | Typical Cost |
|---|---|
| Ready-made standard blackout curtains (pair) | £25 to £70 |
| Ready-made ultra blackout curtains (pair) | £50 to £120 |
| Blackout lining added to existing curtains | £25 to £50 per window in materials |
| Room-darkening pole/track upgrade | £20 to £80 extra |
Frequently Asked Questions
What is a blackout curtain?
A blackout curtain is made with or lined with a densely woven or coated fabric that blocks light, typically eliminating 85% to 99% of light depending on the specific fabric grade.
Are blackout curtains a good idea?
For most bedrooms and nurseries, yes, given the sleep, privacy, thermal, and sound benefits, though fabric alone cannot fully replicate the total darkness of a well-fitted blind flush to the window.
Is it blockout or blackout?
Both describe the same product; “blackout” is the standard UK term, while “blockout” is used more commonly in some other markets, such as Australia.
What are alternatives to blackout curtains?
Blackout roller blinds, Roman blinds, and shutters are the main alternatives, with flush-fitted roller blinds generally achieving the most complete darkness since they avoid the fabric edge gaps inherent to curtains.
Expert Insight
Curtain retailers consistently note that the biggest source of customer disappointment with blackout curtains is not the fabric grade but unmanaged gaps at the sides and top of the window, which is why pairing a genuinely good blackout fabric with adequate pole width and a pelmet delivers a far better real-world result than fabric grade alone.
Final Thoughts
Blackout curtains genuinely improve sleep conditions, privacy, and thermal comfort, but getting the best real-world result depends as much on hardware width and return depth as it does on the fabric’s blackout percentage. Where total darkness is essential, such as a nursery or a shift worker’s bedroom, pairing curtains with a flush-fitted blackout blind is worth considering over curtains alone.
Buying blackout curtains? Choose a pole or track at least 15cm wider than your window frame on each side, since this single adjustment does more for real-world darkness than upgrading fabric grade alone.
Related Guides
- Curtain Linings: The Complete Guide
- Curtain Types & Styles: The Complete Guide
- Eyelet Curtains: The Complete Buying Guide
Written by the HometoWorld editorial team. HometoWorld covers home improvement, renovation, and property maintenance across the UK, with guides written and fact-checked against current UK soft furnishing industry standards and retailer specification data. This article draws on trade fabric grading standards and independent comparison of curtains against blind and shutter alternatives, rather than promoting one retailer’s product range.
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