How this works
Tile quantity is just (total area / per-tile area), padded by a waste factor for cuts, breakages and pattern matching. The waste factor depends on layout: about 10% for a straight grid where most cuts are at the edges; 15% for a diagonal layout where every edge tile needs a 45° cut; 20% or more for complex patterns like herringbone, mosaic borders, or rooms with lots of obstacles (toilets, columns, alcoves). Buying short and having to come back for a second box that turns out to be a different shade lot is the worst-case mistake — most installers err on the side of 1–2 extra boxes for any large job.
The area you tile isn't always the floor footprint. For walls, multiply wall length by ceiling height, then subtract door and window openings. For backsplashes, work in linear feet × backsplash height. For floors with built-in cabinets or fixtures, you can subtract those areas, but most installers just tile under and around — it's easier and the extra cost is small relative to the labour.
The formula
Areas in matching units. The ⌈ ⌉ symbol means round up — you can't buy a fractional tile or a fractional box. Per-tile area uses the same units as the room area; this calculator handles the metric/imperial unit mix automatically.
Example calculation
- Floor 4 m × 3 m = 12 m². Tiles 30 × 30 cm = 0.09 m².
- Tiles needed = 12 / 0.09 ≈ 134. Plus 10% waste = 148. Boxes (10/box) = 15.
Frequently asked questions
How much waste should I budget?
Standard guidance: 10% for a square grid, 15% for diagonal, 20% for herringbone or rooms with many obstacles. Add 5% extra for natural stone (more breakages and shading variation). For very small jobs (< 5 m²) use a flat 15% minimum since cut waste dominates.
Why round up to whole boxes?
Tile retailers sell by the box; loose-tile sales are rare and the loose tiles often come from a different batch with subtle colour or shade differences. Buying full boxes — and from a single dye lot — keeps colour consistent across your installation. Save the leftover tiles for future repairs since matching a discontinued lot years later is essentially impossible.