How Many Tiles Do I Need for a Floor? (Step-by-Step)

A floor is the one surface where a small mistake costs the most, because you find out when half the room is already laid and the dye lots no longer match. This guide is the whole calculation in order, with real numbers.

The short version: measure the room, subtract what you are not tiling, divide by one tile’s area, then add waste for the pattern. Everything below is that sentence with the parts that actually change the answer.

Step 1 — Measure the room, not the tile

Measure length and width along the walls at floor level, at two points each, and use the larger number. Old houses settle; a “12 ft” room is often 12 ft 2 in at one end.

Write down the net area you plan to cover, not the floor plan’s headline number:

Step 2 — Decide what you are NOT tiling

Fixed units do not get tile under them: a galley cabinet run, a kitchen island that never moves, a bathtub footprint, a built-in wardrobe. Subtract those, because tile hidden under a permanent object is money spent on nothing.

Leave in anything that might move or that you tile around: doorways, vents, floor registers, the last row beside a cabinet that a future remodel could pull out. When in doubt, keep the area — the waste buffer is cheaper than a second delivery.

Thresholds, transitions and the strips beside doors are cut pieces, not deductions. They still consume full tiles.

Step 3 — Divide by the tile

Take the net area and divide by the area of one tile.

A 12×12 in tile covers exactly 1 sq ft, so 168 sq ft is 168 tiles before waste. A 6×6 in tile covers 0.25 sq ft, so the same floor is 672 tiles — the pattern cost does not change, but the number of cuts does.

168 ÷ 1 = 168 tiles

Watch the units. If you measured in metres, the tile must be in metres too: 600×600 mm is 0.6 m × 0.6 m = 0.36 sq m, not 3.6.

Step 4 — Set waste by pattern

This is where floors diverge. Every layout that is not a plain stacked grid eats extra tiles on every row that is offset.

So the 168 tiles above become 168 × 1.15 = 194 tiles in an offset layout. Pattern-aware waste is the difference between a floor that finishes and a floor that stops a week short of a discontinued run.

Step 5 — Convert to boxes

Tiles come in boxes and you cannot buy a fraction. If the box holds 10 pieces, 194 tiles is 19.4 boxes — order 20.

Add one box on top if the run is small or the tile is a special order. Dye lots drift between batches, and a repair patch two years later that is a half-shade off is visible across the whole room.

Common mistakes

• Measuring the floor plan instead of the room. Plans show nominal sizes; walls do not.
• Deducting the cabinet you might move later. If there is any chance it goes, keep the tile.
• Using one waste number for every layout. A straight grid and a diagonal are five to ten points apart.
• Forgetting the threshold and the register cuts. They are small, frequent, and always come out of the same box.
• Ordering exactly what the math says. Rounding down to save one box is the usual reason a job stalls.

Worked example, end to end

A 12×16 ft living room with a fixed hearth, 12×12 in tile laid in offset:

• Net: 192 − 24 = 168 sq ft
• Tiles: 168 ÷ 1 sq ft = 168 × 1.15 = 194 tiles
• Boxes: 194 ÷ 10 = 19.4 → 20 boxes
• Grout and adhesive: worked out from the tile size and gap you enter — an offset 12×12 with a 3 mm joint needs roughly 4–5 kg of grout per 100 sq ft

Enter the room and the hearth as separate sections and the tool keeps each deduction and waste rule intact while returning one combined tile, box, grout and cost total.

Use the floor tile calculator to run your own numbers, or read the shower calculation guide if the floor runs into a tiled shower.