Diagonal (45 degrees) Tile Calculator

A standard grid rotated 45 degrees to the walls, so the tiles read as diamonds. Budget about 15% waste rather than the usual 10% — every tile meeting a wall is cut on the diagonal, and a triangular offcut only fits the opposite corner of the room — sometimes.

Your diagonal (45 degrees) layout

Room width (ft)

Room length (ft)

Tile size

Every common tile size, from 2x2 mosaic to 24x48 large format.

Layout pattern

Picking a pattern sets the recommended waste factor.

Waste factor (%)

Tiles per box

Check the box label — it varies by brand.

Tiles to buy

69 tiles

Area to cover: 120 sq ft
Area including waste: 138 sq ft
Tile size: 12 x 24 in
One tile covers: 2 sq ft
Boxes needed: 9 boxes
Waste applied: 15%

Tile is sold by the box — round up and keep one spare box from the same dye lot.

Diagonal (45 degrees) tile needed, with waste

Square footage to order for a diagonal (45 degrees) layout at 15% waste

Area	Plain sq ft	With 15% waste	Extra vs a straight grid
Backsplash (30 sq ft)	30 sq ft	35 sq ft	2 sq ft
Small bathroom (40 sq ft)	40 sq ft	46 sq ft	2 sq ft
Bathroom (80 sq ft)	80 sq ft	92 sq ft	4 sq ft
Kitchen (120 sq ft)	120 sq ft	138 sq ft	6 sq ft
Living room (180 sq ft)	180 sq ft	207 sq ft	8 sq ft

The last column is what the pattern costs you in extra material over a plain grid — usually a good deal less than people fear, and worth knowing before you rule the pattern out.

Where the waste comes from

Every tile meeting a wall is cut on the diagonal, and a triangular offcut only fits the opposite corner of the room — sometimes.

Waste is not a safety margin you can shave. It is a count of tiles that physically cannot be used, and it is set by the geometry of the pattern against the shape of your room. A long narrow room has more perimeter per square foot than a square one and wastes more of any pattern; a room with a bay, an island or several doorways wastes more again.

Keep the offcuts until the job is signed off. On a patterned floor the leftover wedges from one wall are sometimes exactly what the opposite wall needs, and the difference between 15% and 20% waste is often just whether someone bothered to sort them.

Other layout patterns

Comparing layouts before you commit? The tile pattern calculator puts them side by side, and the waste calculator works the allowance from your room shape rather than from a rule of thumb.

Do this math on the job site — in the free app

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Tools the pros use for this job

Levelling System
Levelling System
Angled and interlocking layouts have more edges meeting at odd points, which is where lippage shows.
View on Amazon
Angled and interlocking layouts have more edges meeting at odd points, which is where lippage shows.
Wet Tile Saw
Wet Tile Saw
Diagonal (45 degrees) needs repeatable angled cuts, which a snap cutter cannot make cleanly.
View on Amazon
Diagonal (45 degrees) needs repeatable angled cuts, which a snap cutter cannot make cleanly.
Tile Spacers
500 Pcs 3 mm (1/8 Inch) Plastic Tile Spacers for Stone and Ceramic Tile | 500-Piece Pack,3 mm Spacing,Even Tile Layout,Plastic Construction,Multiple Installation Uses
Check price on Amazon
The joint width is part of this pattern's geometry, not an afterthought.

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How this calculator works

Work out the plain square footage of the area first, then apply the pattern's waste factor on top. For diagonal (45 degrees) that is about 15%, against 10% for a straight grid.

Every tile meeting a wall is cut on the diagonal, and a triangular offcut only fits the opposite corner of the room — sometimes.

A diagonal layout makes an out-of-square room obvious rather than hiding it, which is the opposite of what people expect. The cut tiles along each wall taper visibly if the walls are not parallel. Check the room for square before choosing diagonal over a straight grid.

Dry-lay a section before committing. Two square metres set out on the floor tells you more about how the pattern meets your walls than any calculation, and it is the cheapest possible time to discover that the room is out of square.

Frequently asked questions

How much waste should I allow for a diagonal (45 degrees) layout?

About 15%, compared with 10% for a straight grid. Every tile meeting a wall is cut on the diagonal, and a triangular offcut only fits the opposite corner of the room — sometimes. Order it all in one go: a second order weeks later can come from a different production lot, and on a patterned floor a shade difference between lots is far more visible than it would be on a plain one.

What tile suits a diagonal (45 degrees) pattern?

Any square tile, most commonly 12x12 and 18x18. A diagonal layout makes an out-of-square room obvious rather than hiding it, which is the opposite of what people expect. The cut tiles along each wall taper visibly if the walls are not parallel. Check the room for square before choosing diagonal over a straight grid.

Is diagonal (45 degrees) harder to install than a straight grid?

Yes, and the difficulty is in the setting out rather than the cutting. A straight grid forgives a small error because it accumulates along one axis; a pattern accumulates error in two directions at once and it becomes visible quickly. Snap chalk lines for the whole field before laying anything, and check back to them every few rows rather than trusting the spacers.

Does diagonal (45 degrees) need more grout?

It depends on the tile rather than the pattern — grout follows the joint length per square foot, which is set by the tile size and joint width. What the pattern changes is how much tile you buy, not how much grout each square foot needs. Size the grout from the tile dimensions with the grout calculator.

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Last updated: August 26, 2026 · Reviewed by the Smart Tile Calculator editorial team