Tile Calculator – How Many Tiles Do I Need?
Work out tiles, boxes, adhesive and grout for a floor or wall, with the right waste allowance built in.
Tile Calculator
What are you tiling?
600 × 300mm porcelain with 3mm joints — needs a thicker adhesive bed than wall tiles.
Measure rectangles length by width. Split an L-shape into two rectangles, or measure a circle straight across its widest point.
Measure the area to tile
15 m²
Odd-shaped garden? Split it into rectangles, triangles and circles — we add them up for you.
You need
92tiles
15 m² plus 10% waste — that's 12 boxes
- Boxes to buy
- 12
- Tiles per m²
- 5.6
- Adhesive
- 5 × 20kg bags
- Grout
- 3.6 kg
How we worked this out
Your shopping list
12 × boxes of 600 × 300mm tiles (8 per box)
Buy one spare box and keep it — ranges get discontinued.
£360
5 × 20kg bags of tile adhesive
About 99kg at 6kg per m².
£80.00
1 × 5kg bags of grout
£14.00
1 × bags of 3mm tile spacers
£4.00
Tiles per square metre by UK tile size
| Tile size | Tiles per m² | Typical use |
|---|---|---|
| 100 × 100mm | 100 | Small mosaics and splashbacks |
| 200 × 100mm | 50 | Metro / brick bond walls |
| 300 × 200mm | 16.7 | Bathroom walls |
| 300 × 300mm | 11.1 | Small floors and shower trays |
| 600 × 300mm | 5.6 | Floors, large walls |
| 600 × 600mm | 2.8 | Large-format floors |
How this calculator works
First we total the area you enter. Then we add the waste allowance — 10% for a straight layout, 15% for diagonal or herringbone, because angled cuts waste far more tile.
We divide that figure by the area of a single tile to get the number of tiles, then divide by the tiles per box and round up, because tiles are sold by the box.
Adhesive is estimated at 4kg per m² for wall tiles and 6kg per m² for floors, which reflects the thicker bed a floor needs. Grout is worked out from tile size, joint width and tile thickness — smaller tiles and wider joints both mean more grout.
Worked example: a 3m × 2m bathroom floor
A 3m × 2m floor is 6m². Adding 10% gives 6.6m² of tiles to buy. With 600 × 300mm porcelain — 0.18m² per tile — that's 6.6 ÷ 0.18 = 37 tiles. At eight tiles per box you need five boxes, which gives 40 tiles and three spare.
Adhesive: 6.6m² × 6kg = 40kg, so two 20kg bags. Grout with 3mm joints on 9mm-thick tiles works out at roughly 6kg — two 5kg bags. Add a bag of 3mm spacers, a tub of silicone for the perimeter, and a tile cutter if you don't own one. Budget around £180–£220 all in for a mid-range porcelain.
Tips from the trade counter
- Check the batch numbers. All your boxes should carry the same batch or shade code. Different batches can be visibly different colours.
- Dry-lay the first row. Set out so you don't end up with a 10mm sliver of tile in the most visible corner of the room.
- Prime the substrate. Plasterboard, screed and old adhesive beds all need priming or the adhesive fails early.
- Use flexible adhesive and grout on floors. Especially over timber or underfloor heating, where movement is guaranteed.
- Silicone, not grout, in the corners. Internal corners and the joint between wall and bath move — grout there will always crack.
Floors, weight and underfloor heating
Tiling a timber floor needs a rigid, well-screwed substrate — usually 6mm tile backer board or a minimum 18mm ply overlay — plus flexible adhesive. A suspended floor that bounces will crack tiles and grout, whatever adhesive you use.
Over underfloor heating, leave the screed to cure fully and commission the heating slowly before tiling. Use a decoupling mat with large-format tiles. If you're unsure about the floor's load capacity, ask a builder before committing to heavy natural stone.
Frequently asked questions
How many tiles do I need?
Divide the area to be tiled by the area of one tile, then add 10% for cuts and breakages (15% for diagonal or herringbone layouts). Our calculator rounds up to whole boxes.
How much waste should I allow for tiling?
10% for a standard straight layout, 15% for diagonal, herringbone or a room with lots of cuts, and up to 20% for patterned tiles that need matching.
How much tile adhesive do I need?
Roughly 4kg per m² for wall tiles at a 3mm bed and about 6kg per m² for floor tiles at 6mm. Large-format tiles need a thicker bed, so allow more.
How much grout do I need?
It depends on tile size and joint width — typically 0.5kg per m² for small wall tiles with 2mm joints, and 1.5–3kg per m² for floor tiles with 3–5mm joints. The calculator works it out from your figures.
What size grout joint should I use?
2mm for rectified wall tiles, 3mm for standard ceramics, and 3–5mm for floor tiles and natural stone. Wider joints absorb small size variations between tiles.
Should I buy an extra box of tiles?
Yes. Buy one spare box and keep it. Tile ranges are discontinued constantly, and a cracked tile in three years' time is otherwise a whole new floor.
Can I tile over existing tiles?
On walls, yes, if the existing tiles are sound, clean and firmly stuck — use a suitable primer. On floors it's riskier because of height and loading; lifting the old tiles is usually the better job.