Slimline venetian blinds, the ones with 25mm slats, are the better fit for most small windows, kitchens and bathrooms. Once a window gets wide, or you want a clearer view out with the slats open, 50mm slats look calmer and let more of the outlook through. Reveal depth and window handles often settle the question before style comes into it.
What slimline actually means
Slimline is the trade name for a venetian with 25mm slats, usually in aluminium. It is the blind most people picture when they hear the word venetian: fine metal slats in a kitchen or an office window.
Across the industry, slat widths commonly run from 16mm up to 63mm. Aluminium is mostly seen at 25mm, with 50mm as the wide option. Timber and PVC are most often 50mm, and timber ranges commonly add 35mm and 63mm.
This guide sticks to 25mm against 50mm, because that is the choice most houses come down to.
How slat width changes the view
Wider slats mean fewer slats. Over the same drop, a 50mm blind has roughly half as many slats as a 25mm one, so with the slats open you look through fewer lines and bigger gaps.
That is why a living room window that looks onto a garden usually suits 50mm. Slimline slats across a big pane of glass read as a fine grey screen. That works in a study and looks a bit busy in a lounge.
Tilted shut, there is not much between them for privacy. The difference shows when the slats are open, and in how the blind looks from across the room.
Reveal depth and window handles
A venetian slat swings through its full width every time you tilt it. So a 50mm slat needs a bit more than 50mm of clear depth inside the reveal, measured to the nearest handle, lock or frame. A 25mm slat needs about half that.
Shallow reveals are where slimline helps most. Plenty of Sydney units have aluminium windows sitting close to the face of the plaster, and older houses often have winder handles on awning windows poking into the reveal. A 25mm blind will often fit inside those openings where a 50mm one would knock the handle on every tilt.
If you want the wider slat and the reveal is too shallow, fix the blind to the wall or architrave instead. Our guide on how to measure for venetian blinds shows how to check the depth properly.
Stack height when the blind is up
Pull a venetian all the way up and the slats pile into a stack under the headrail. Stack height has more to do with material than width. Thin aluminium slats pack down tight, while thicker timber and PVC slats stack deeper.
On a tall window, a deep stack takes a noticeable band off the top of the glass. If you want the whole window clear during the day, the blind can be fixed above the opening so the stack sits against the wall.
Getting the proportion right
Small slats suit small windows. A 50mm slat on a narrow bathroom window looks chunky, and a 25mm slat across a wide living room window looks busy. Matching the slat to the size of the glass is most of the style decision.
As a rough guide:
- Bathrooms, laundries and small kitchen windows: 25mm, usually aluminium.
- Bedrooms: either works, so let the reveal depth and the rest of the house decide.
- Living rooms and big windows: 50mm, in aluminium, timber or PVC.
- Studies: 25mm if you want fine control over glare on a screen.
Keep one width through a room where you can. Two windows side by side with different slats never quite line up, and the eye picks it straight away.
| Feature | 25mm slimline | 50mm slat |
|---|---|---|
| Usual material | Aluminium | Aluminium, timber or PVC |
| Best on | Small windows, kitchens, bathrooms | Wide windows, living areas |
| View with slats open | More lines, finer gaps | Fewer lines, clearer outlook |
| Reveal depth needed | Copes with shallow reveals | Needs a bit more than 50mm clear |
| Across a big window | Can look busy | Calmer and more solid |
Where material comes into it
If you want the look of a wide slat in a damp room, 50mm aluminium is worth a look. It gives the bigger slat without any worry about steam, which helps in a large bathroom or a kitchen with a wide window. Our guide to bathroom venetian blinds covers wet rooms in more detail.
For living areas and bedrooms where the timber look matters, wooden venetian blinds in a 50mm slat are the usual choice. They suit timber floors and older homes with deep reveals.
Slat width is easy to get wrong from a brochure and easy to get right at the window. We make our venetian blinds in our own Sydney factory, and Steve measures every job himself and brings the samples, so you can hold both widths against your own glass. Book a free measure and quote and settle it at the window rather than from a photo.
Common questions
Are slimline venetian blinds the same as 25mm venetians?
Yes. Slimline is the trade name for a venetian with 25mm slats, and it is almost always aluminium. Some ranges also make a narrower slat for very small or shallow windows, but 25mm is what most people mean.
Do wider slats let in more light?
With the slats open, a little. A 50mm blind has fewer slats over the same drop, so the gaps are bigger and the view is clearer. Tilted shut, there is very little difference between the two.
Will a 50mm venetian fit in a shallow reveal?
Only if there is a bit more than 50mm of clear depth to the nearest handle, lock or frame, because the slats need room to tilt. If there is not, go to a 25mm slat or fix the blind outside the reveal.
Can I mix slat widths in the same house?
Between rooms, yes, and it often makes sense to use 25mm in the bathroom and 50mm in the living room. Within one room, or on windows you see together, keep to one width so the lines match.
Which width is easier to keep clean?
A 50mm blind has fewer slats to wipe, so it is quicker. Slimline aluminium wipes down easily with a damp cloth, but there are about twice as many slats on the same window.