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What is the 3/4/5 rule for tiling
Short description: The 3/4/5 rule is a simple layout method used to create a perfect 90-degree angle before tiling. It helps ensure tiles run straight, grout lines stay aligned, and cuts remain even, saving time, tiles and costly mistakes.
If you’ve ever started tiling and realised halfway through that something feels slightly off, chances are your layout wasn’t square to begin with. Walls aren’t always straight, floors aren’t always level, and corners definitely can’t be trusted.
That’s where the 3/4/5 rule comes in. It’s a simple measuring trick that helps you square up your layout before the first tile goes down.
No fancy tools. No trade-only secrets. Just a reliable way to avoid crooked tile lines, skinny cuts and that slow sinking feeling when you notice everything drifting sideways.
So if you’re planning a bathroom, kitchen or outdoor tiling project, understanding this 3/4/5 rule for tiling can save you time, tiles and money.
What is the 3/4/5 rule for tiling
In short, the 3/4/5 rule for tiling is when one side of a triangle measures three units, the other side measures four units, and the diagonal between them measures five units, the angle between the two sides is exactly 90 degrees.
The 3/4/5 rule is a basic method for creating a perfect right angle. It’s based on a simple mathematical principle that tradies have used for decades, long before laser levels were common.
Those units can be anything. Metres. Feet. Tile widths. Even tape-measure lengths. The ratio is what matters, not the size.
When tiling, this rule helps you set out a square reference line so your tiles run straight across the room instead of slowly creeping off course.
Why the 3/4/5 rule matters for tiling
Tiles don’t forgive mistakes. A few millimetres out at the start can turn into centimetres by the time you reach the opposite wall.
It’s extra handy in older homes, where nothing is truly square, and in open areas where long tile runs make any error obvious.
Using the 3/4/5 rule helps you:
• Start your layout square…even if the walls are not.
• Avoid uneven tile cuts along edges
• Keep grout lines straight and consistent
• Reduce tile waste from misaligned layouts
How the 3/4/5 rule works in practice
You don’t need to overthink it…the process is straightforward and works the same way whether you’re tiling a bathroom floor or a large outdoor area.
1. First, choose a starting point. This is usually the most visible wall or the centre of the room, depending on your layout.
2. From that point, measure a straight line in one direction. This will be your 3-unit side.
Next, from the same starting point, measure another line at roughly 90 degrees to the first. This will be your 4-unit side. Don’t worry if it’s not perfectly square yet.
3. Now measure the distance between the ends of those two lines.
If that diagonal measurement is exactly five units, your angle is square.
4. If it’s more or less, adjust the second line until it hits that 5-unit mark.
Once it does, you’ve got a perfect right angle and a reliable reference line to start tiling from.
What measurements should you use?
The beauty of the 3/4/5 rule is flexibility. You can scale it up or down depending on the size of the space!
For small bathroom tiles or splashbacks, you might use 300 mm, 400 mm and 500 mm. For larger floors or outdoor areas, 3 metres, 4 metres and 5 metres are more practical.
You can even use objects, such as the length of a tile, provided you use the same side of the tile each time.
Cheapestiles Tip: Bigger measurements usually give better results because small errors are easier to spot and correct.
When you should use the 3/4/5 rule
Not every tiling job needs it, but in most cases, it’s worth the few extra minutes upfront.
Even experienced tilers use this method on a regular basis. It’s one of those simple habits that prevents bigger problems later.
When you might use the 3/4/5 rule:
• Tiling floors in bathrooms, kitchens or laundries
• Laying large format tiles where lines must stay straight
• Working in older properties or rooms with uneven or out-of-square walls
• Tiling outdoor patios or alfresco areas
• Installing feature tiles where alignment matters visually
Common mistakes when using the 3/4/5 rule
Like anything, the 3/4/5 tiling rule only works if it’s done correctly.
A few common slip-ups can throw things off.
- One mistake is measuring from the wall instead of a reference line. Walls are rarely straight, so always trust your measurements, not the room.
- Another is using measurements that are too small. The shorter the lines, the easier it is to be slightly off without noticing. Scaling the rule up improves accuracy.
- Rushing the setup is another issue. Spending five extra minutes checking your square can save hours of rework later.
How the 3/4/5 rule fits into tile layout planning
The rule is just one part of a good tile layout plan.
Before you start tiling, you should also dry-lay a row of tiles to see how cuts will land at the edges. This helps you avoid thin slivers of tile along walls or doorways, which not only look awkward but are also harder to cut and install cleanly.
Once your square lines are set, you can adjust your layout slightly to balance cuts on both sides of the room. That way, the finished result looks intentional rather than squeezed in.
Does the 3/4/5 rule work for wall tiling?
Yes, it does. While it’s most commonly used on floors, the same principle applies to walls, especially in showers and splashbacks. Vertical tile lines need to be straight, too, and starting square helps everything stack neatly upward.
This is particularly important with subway tiles, kit kat tiles or any layout where alignment is obvious.
Is the 3/4/5 rule DIY friendly?
The 3/4/5 rule itself is very DIY friendly… If you can measure accurately and take your time, you can absolutely use it at home.
That’s why the main rule for the 3/4/5 tile rule is that patience pays off. That said, layout is only part of the tiling process.
Waterproofing, substrate prep and correct installation techniques still matter. If you’re unsure, seeking advice early from one of our expert tile specialists can save you from costly fixes later.
Why choose Cheapestiles
At Cheapestiles, we know tiling isn’t just about picking a tile you like.
It’s about planning, layout and making wise decisions that help the job go smoothly from start to finish.
Whether you’re tackling a small bathroom, a kitchen splashback or a whole outdoor area, our range of affordable tiles gives you options that work with real-world homes, not perfect showrooms. If you need help choosing tiles that suit your space or want advice on quantities, layout or the 3/4/5 tiling rule, our team is always happy to help.
Call 02 9790 4273 or email info@cheapestiles.com.au
Still not sure how many tiles you need?
Use our free tile calculator to get an instant estimate in square metres and then add a 10% buffer for offcuts, layout changes or sneaky mistakes. Got an oddly shaped room or complex layout? Give us a call. We’re happy to walk you through it. Call 02 9790 4273 or email info@cheapestiles.com.au and let’s get your Moroccan tile project squared away.