Tile Calculator
Enter the area in metres and your tile size in millimetres to see how many tiles and boxes to buy, plus adhesive, grout and an estimated cost in GBP.
Formulas shown on this page · Last reviewed October 2026
How the tile calculator works
tiles = area ÷ ((tile width + joint) × (tile height + joint)) × (1 + waste)
boxes = tiles × tile area ÷ box coverage, rounded up
Sizes are in millimetres and the grout joint is added to each tile so the layout is not under-counted. Popular sizes in the UK include 300 × 600 mm, 600 × 600 mm and 750 × 750 mm, available from tile shops and builders’ merchants. Your default tile of 600 × 600 mm covers 0.36 m².
Waste allowance by layout
| Layout | Extra to order |
|---|---|
| Straight (grid) | 10% |
| Diagonal | 15% |
| Herringbone | 15% |
Cuts, breakages and awkward corners all use tiles. Buy a little extra for future repairs – dye lots can vary between batches.
Adhesive and grout
Flexible tile adhesive is sold in 20 kg bags; large-format tiles are usually back-buttered and laid with a 10–12 mm notched trowel. The default coverage of 4 m² per 20 kg bag is only an approximation; real coverage depends on trowel size, tile size and how flat the surface is, so check the bag. Grout is estimated from joint length, joint width and tile thickness with 10% extra, and is also approximate. Check that floorboards or screeds are flat and stiff enough; underfloor heating needs a flexible adhesive and grout.
Prices are typical – check local prices and replace them with your own quotes.
Frequently asked questions
How many 600 × 600 mm tiles do I need for 12 m²?
With 3 mm joints and 10% waste you need 37 tiles, which is 10 boxes at 1.44 m² per box. With a diagonal layout (15% waste) it rises to 38 tiles.
How much does it cost?
At £30.00 per m², 10 boxes (14.4 m²) cost about £432.00, before adhesive and grout.
How many bags of adhesive for 12 m²?
At roughly 4 m² per 20 kg bag you need about 3 bags. This is an estimate; large tiles and uneven floors use more.
Why add waste when the area is exact?
Edge cuts rarely reuse the offcut, and diagonal or herringbone patterns create many more small cuts, hence the higher 15% allowance.