Two mistakes cost renovators real money on tiles: ordering short, and topping up later. The first stalls your tiler mid job. The second lands you a box from a different factory batch that is a shade off the rest of your floor, and you will see the line where the batches meet forever. Both are avoidable with ten minutes of measuring and one rule.
Step 1: measure up in square metres
Floors: length times width, in metres. A 2.4m x 1.8m bathroom floor is 4.32 m². For an L-shaped room, split it into two rectangles and add them.
Walls: width times height for each wall you are tiling, added together. Only subtract openings bigger than a door. Windows, niches and vanities feel like they should reduce the count, but the offcuts around them are rarely reusable, so leaving them in gives you a built-in buffer exactly where the fiddly cuts happen.
A worked example, a typical small bathroom:
Floor: 2.4m x 1.8m = 4.3 m²
Shower walls: two walls at 1.0m x 2.4m high = 4.8 m²
Feature wall behind vanity: 1.8m x 2.4m = 4.3 m²
Total tiled area: 13.4 m²
Step 2: add 15% for wastage
The 15% covers three things that happen on every job, not just bad ones:
Cuts. Every edge, corner, floor waste and tap penetration eats part of a tile, and most offcuts cannot be used elsewhere.
Breakage. A couple of tiles in any order will chip in transit or crack during cutting. That is normal, and it is why the buffer exists.
Pattern matching. Laying patterns multiply offcuts. A straight lay on a big open floor with a 450x450 tile like Lorne might scrape by on 10%, but herringbone or diagonal work with a subway like Mildura can chew through 20%. If you are unsure, 15% is the number that almost never leaves you short.
Back to the example: 13.4 m² x 1.15 = 15.4, so you order 16 m². Rounding up to the next whole box is always correct. Rounding down is how top-up orders happen.
Why you order it all at once: batch matching
Tiles are fired in batches, and every batch comes out fractionally different. Kiln temperature drifts a few degrees, the glaze mix changes, and the "same" tile from a different firing lands a shade lighter or darker. Factories print a batch and shade code on every box for exactly this reason.
One order from us equals one factory batch. Order your 16 m² together and every tile matches. Order 14 m² now and 2 m² in a month, and the top-up will almost certainly come from a new batch. On a plain white wall you might get away with it. On a large-format travertine look like Hobart Ivory, the join line is visible from the doorway.
The leftover boxes are not waste either. A few spare tiles from the original batch are the only perfect repair stock you will ever have if a tile cracks in five years.
Cannot be bothered with the maths? Reply to any of our emails with your room sizes and the tile you are looking at, and we will do the quantities for you the same day. We answer these ourselves, every day.
Quick reference
Straight lay, large tiles, open floor: add 10 to 15%
Standard bathroom with cuts and corners: add 15%
Herringbone, diagonal or small formats like Wilsons kit kat: add 20%
Always: round up to the next full box, order in one go
Still choosing between tiles? Start with 3 samples for $5 and our guide on how to test a tile sample at home. And if you want to know why the same tile costs 40 to 70% more in a showroom, we broke down the chain dollar by dollar.