How this works
Estimating flooring is mostly two numbers: the net floor area, and a waste allowance on top. The geometry is the easy part — for a rectangular room it's just length × width, and for L-shaped or stepped rooms you split the floor into rectangles, calculate each, and add them. Subtract any fixed obstructions you won't be tiling around (a kitchen island base, a built-in bath) but don't bother subtracting cabinets that sit on the floor, since you tile under them in case of future replacement.
The waste allowance is what separates a smooth job from a panicked Saturday morning trip to the merchant. The standard rule is 10% for a square or rectangular room laid in a straight pattern. Bump that to 15% for diagonal or herringbone layouts (more cuts at the perimeter), 20% for highly patterned rooms with feature borders, and 5% only if you have a very square room and a forgiving tile pattern. The waste covers three things: cuts at the perimeter (the offcut from one cut is rarely usable elsewhere), breakages during handling and installation, and the spare you keep for repairs years later when the manufacturer has long since discontinued the line.
A few practical points. (1) Always buy from one batch — tiles, laminate planks and vinyl all vary slightly in shade between production runs, and a mid-floor switch is permanently visible. Order the full quantity at once, including spares. (2) Tile count vs box count are different things. Tiles ship in boxes, often 1 m² or thereabouts, but yields vary by tile size — the calculator gives you tile count, and you should round up to the next whole box at the merchant. (3) For laminate and vinyl planks, the "tile size" math still works — just enter the plank dimensions. Click-system laminate has slightly higher waste than tile (12-15% is normal) because end cuts on planks are often unusable.
The formula
A is the net floor area in your chosen units (m² or ft²). waste% is your over-order margin: 10% straight-laid in a square room, 15% diagonal/herringbone, up to 20% for patterned rooms. Tile dimensions can be in centimetres (metric) or inches (imperial); the calculator handles unit conversion internally so the count is always correct. Tile count rounds up — you can't buy half a tile.
Example calculation
- Bathroom: 3 m × 2.4 m. Tiles: 30 cm × 30 cm. Straight pattern, 10% waste.
- Net area = 3 × 2.4 = 7.2 m². With 10% waste = 7.92 m² to order.
- Tile area = 0.30 × 0.30 = 0.09 m². Tile count = ceil(7.92 / 0.09) = 88 tiles.
- Round up to whole boxes at the merchant — typically 88 tiles ≈ 8 m² boxes (≈ 9 boxes if 11 tiles per box).
Frequently asked questions
How much waste should I add — 10%, 15%, or more?
Start with 10% as a default for a rectangular room laid in a straight pattern with rectangular tiles aligned to the walls. Move to 15% if you're laying diagonally, in a herringbone or chevron pattern, or if the tile has a strong directional pattern that constrains how offcuts can be reused. Push to 20% for rooms with feature borders, mosaic insets, or unusual shapes (lots of nooks and recesses). Drop to 5% only if you have a very square room, large simple tiles (no pattern matching needed), and you're comfortable with no spares for future repairs. Going under 10% on a real-world job is a false economy — the cost of one extra box at install time is negligible compared to the cost of a half-finished floor when you run out 30 minutes from finishing.
Do I subtract cabinets, the toilet, or built-in furniture?
No, with one exception. The standard practice is to tile (or lay flooring) under everything that sits on the floor, even base cabinets and bath panels — partly because if those units are ever replaced, you don't want a tiled "footprint" of the old layout, and partly because cutting around every kick-board doubles your perimeter cuts and waste. Subtract only fixed structural obstructions: a kitchen island that is bolted to the floor and includes its own base, a built-in bath with tiled apron, a structural column. The toilet itself is usually unbolted and re-seated on top of the new floor, so include the area under it in your total. If you're unsure, include it — over-ordering by a square metre is much cheaper than a future patch repair.
How does this work for laminate or vinyl planks instead of square tiles?
The same maths works — enter the plank dimensions where the tile dimensions go (e.g. 19 cm × 128 cm for a typical laminate plank). Two adjustments are worth knowing. (1) Bump the waste up to 12-15% rather than 10%. End cuts on planks are often unusable because click-systems require a minimum plank length, and you also need to stagger end joints between rows by at least 30 cm, which forces extra cuts. (2) Order in full packs from the merchant — laminate ships in packs of 6-10 planks covering ~2 m², and you can't buy individual planks. The calculator gives you plank count; round up to the next whole pack. For very narrow rooms (under one plank wide) a different layout calculator may be more useful — you'll be cutting the length of each plank rather than the count.
Why not just buy the exact tile count?
Three reasons, in order of importance. (1) Cuts: the offcut from one edge cut is rarely usable elsewhere — different angle, wrong size — so every perimeter cut effectively wastes a tile. The waste % covers this. (2) Breakage: tiles crack during transport, during dry-laying, and during cutting. Even careful pros lose 2-3% to breakage on a typical job. (3) Spares: years from now you'll want a few tiles to replace a cracked one. Manufacturers discontinue lines, dye lots vary, and matching to a new tile is almost never perfect. Keeping 5-10 spare tiles in the loft is genuinely useful for the next 10-15 years. The combined effect is the standard 10% rule. Buying the exact count is a recipe for either an unfinished floor or a permanently mismatched repair patch later — both of which cost orders of magnitude more than one extra box at install time.