How Many Tiles Do I Need? A UK Tiling Calculator Guide
Published 2026-07-10 · Browse all tools
"How many tiles do I need?" sounds like a simple question, and the maths is. Where people come unstuck is wastage, pattern, and the difference between how tiles are sold and how they're used. Order tight and you're back at the merchant halfway through, hoping the next box is the same batch. Order blind and you've got three unopened boxes going back for a restocking fee. This guide gets you to the right number the first time, for UK tiles sold by the box and the square metre.
For the quick answer, put your room size into the tile calculator. To understand the number it gives you, read on.
Use the Tile Calculator hereThe basic calculation
Tiles in the UK are almost always sold and quoted by the square metre, so you work in m² and let the shop worry about how many individual tiles that is.
Step 1 — measure the area. For a floor: length × width in metres. For a wall: width × height in metres. Add each wall you're tiling.
Step 2 — subtract large openings. Take off doorways, windows and any run you're not tiling, if they're big. A single window on a wall is worth subtracting. A light switch isn't.
Step 3 — add wastage. This is the step people skip. Every job needs spare tiles for cuts, breakages and future repairs.
Step 4 — round up to full boxes. Tiles come in boxes covering a set area, often around 1.0–1.5 m² per box depending on tile size. You can only buy whole boxes, so round up.
How much wastage to add
Wastage isn't padding — it's the tiles that get cut down at edges, snapped in the nippers, or kept back for the day a tile cracks and you need an exact match years later.
As a UK rule of thumb:
- 10% for a straight, square layout on a simple rectangular room. This is the standard minimum.
- 15% for diagonal layouts, brick-bond patterns, or rooms with lots of corners, alcoves and pipe boxings — anything that means more cuts.
- 20% for large-format tiles, herringbone, or highly patterned/rectified tiles where a mismatch is obvious and cuts are less forgiving.
Worked example: a bathroom
Say you're tiling a small UK bathroom. The walls you're tiling total 12 m² before openings, with one window taking out 0.8 m². You're going floor-to-ceiling behind the bath and around the room in a standard straight layout.
Net wall area: 12 − 0.8 = 11.2 m². Add 10% wastage: 11.2 × 1.10 = 12.3 m² of tiles to order. The floor is 4 m², straight layout: 4 × 1.10 = 4.4 m².
If the wall tiles come in boxes of 1.2 m², that's 12.3 ÷ 1.2 = 10.25 → 11 boxes. Floor tiles at 1.44 m² a box: 4.4 ÷ 1.44 = 3.06 → 4 boxes.
At a typical 2026 price of £22–£40 per m² for mid-range ceramic wall tiles and £30–£55 per m² for porcelain floor tiles from B&Q, Topps Tiles or Wickes, the tiles for this bathroom land somewhere around £350–£600 before adhesive, grout and trims.
Don't forget adhesive, grout and trim
The tile count is only part of the shopping list.
Adhesive: coverage depends on tile size and trowel notch, but a 20 kg bag of standard wall-tile adhesive covers roughly 3–5 m². Floor and large-format tiles use more because they need a fuller bed. Check the bag.
Grout: a 5 kg tub covers a lot of small wall tiles but far fewer large floor tiles, because wider joints on big tiles swallow more grout. Buy for your tile size and joint width.
Trim and edging: measure the exposed edges in linear metres and add a length or two for cuts.
The floor build-up underneath — a point most tile guides miss
Before a single floor tile goes down, the surface under it has to be right. On a new or renovated floor, that usually means a screed laid over the sub-base or slab, brought level and left to dry properly.
Two things trip people up here. First, a fresh sand-cement screed can take weeks to dry enough to tile over — roughly a day per millimetre for the first 50 mm — so tiling too early traps moisture and lifts the tiles later. Second, the tile count depends on a flat floor; a wavy screed means thicker adhesive, more cuts and more waste. If you're building up the floor first, size the layer with the screed calculator and check drying time before you order tiles.
Quick reference: tiles per m²
Rough tile counts by common size, before wastage:
- 100 × 100 mm — approx. 100 tiles per m²
- 150 × 150 mm — approx. 44 tiles per m²
- 200 × 200 mm — approx. 25 tiles per m²
- 300 × 300 mm — approx. 11 tiles per m²
- 300 × 600 mm — approx. 5.5 tiles per m²
- 600 × 600 mm — approx. 2.8 tiles per m²