Tile Calculator
Work out exactly how many tiles and boxes you need for a floor or wall, with the right wastage allowance already built in. Add your own tile, adhesive and grout prices for a full cost estimate — nothing here uses a stale national average.
How this calculator works
The calculator divides your total surface area by the footprint of one laid tile — the tile face plus its share of the grout joint on each side — then applies your wastage allowance and rounds up to whole tiles:
tiles = ceil( area ÷ ((tile width + gap) × (tile height + gap)) × (1 + wastage%) )
Skipping the grout gap in the math overstates coverage and undercounts tiles, especially with small tiles and wide joints. This calculator always includes it.
Worked example
A 12 ft × 10 ft floor, 12 in tiles, ⅛ in grout gap, laid in a straight grid:
- Floor area: 12 × 10 = 120 sq ft.
- Each laid tile covers 12.125 in × 12.125 in ≈ 1.02 sq ft including its grout share.
- 120 ÷ 1.02 ≈ 117.6 → 118 whole tiles to cover the floor.
- Add 10% for a straight grid: 118 × 1.10 ≈ 129.8 → buy 130 tiles.
The extra 12 tiles aren't padding — they cover the cuts at the room's perimeter, the one or two that crack during cutting, and a spare box for repairs down the line.
Choosing the right wastage allowance
| Layout | Allowance | Why |
|---|---|---|
| Straight grid | 10% | Cuts only at the room's perimeter |
| Offset / brick bond | 12% | Every other row starts with a cut tile |
| Diagonal (45°) | 15% | Every perimeter tile is an angled cut |
| Herringbone / chevron | 20% | Angled cuts at every edge, offcuts rarely reuse |
Small rooms and rooms with lots of alcoves or fixtures sit at the high end of each range, since the cut perimeter is large relative to the floor area. For natural stone with batch variation, round up rather than down — a later delivery may not match the shade.
Tiling floors, walls, showers and backsplashes
The same formula works for any tiled surface — only the measuring approach changes:
- Floors — measure at skirting-board level and let tile run under each doorway threshold.
- Walls — multiply each wall's width by its tiled height, and only subtract openings larger than about a square foot.
- Showers — tile each enclosure wall separately and add the totals; small mosaic strips push wastage toward 15–20%.
- Backsplashes — measure the run length by the height from worktop to cabinets; expect most tiles to be cut, so round up.
How much does tiling cost?
Rather than quoting a national average that's stale the day it's published, this calculator prices the job from what you actually enter. InBuy the materials mode, give your tile price per square foot, plus adhesive and grout coverage and price per bag — each is itemised and totalled. In Installed price mode, enter a single installer rate per square foot and the area does the rest. Either way, the estimate assumes the surface is already prepared, so backer board, waterproofing and trim aren't included.
Frequently asked questions
How many tiles do I need for a 10×10 room?
A 10×10 ft room is 100 square feet. With 12×12 inch tiles that's 100 tiles before wastage, or about 110 tiles with a standard 10% wastage allowance. Enter your exact room and tile size above for a precise count, since grout gap and layout both shift the number slightly.
How much extra tile should I buy for wastage?
About 10% extra for a straight grid layout, 12% for an offset or brick bond, 15% for a diagonal layout, and 20% for herringbone or chevron. The allowance covers perimeter cuts, breakages, and spares for future repairs from the same batch.
Does grout gap size change how many tiles I need?
Slightly. A wider gap means each tile covers a little more floor including its share of the joint, which marginally lowers the count. The effect is small with large tiles and more noticeable with small mosaics.
How many tiles come in a box?
It depends on the tile size and manufacturer — large-format tiles often ship 3–6 per box, small ceramic tiles can be 10–25 per box. Suppliers list a box either as a tile count or the area it covers, so this calculator accepts either.