How this is worked out
Each tile covers (length + joint) × (width + joint). Tiles needed = area ÷ that, plus your allowance for cuts, rounded up.
Boxes use the m² per box on the label, applied to the area with waste added. Adhesive is area × the kg per m² from your bag, divided by the bag size. We don’t fill in an adhesive figure for you, because it varies too much between products and trowel sizes to guess.
Worked example
A 12 m² kitchen floor in 600 × 300mm tiles with 3mm joints: each tile covers 0.603 × 0.303 = 0.183 m², so 12 ÷ 0.183 = 66 tiles, or 73 with 10% for cuts.
If the box says 1.08 m² (six tiles), that’s 13.2 m² ÷ 1.08 = 13 boxes. With adhesive at 4 kg per m² from a 20kg bag, 48kg is three bags.
Measuring tips
- Measure each wall separately and add them up. Take off windows and doors, but leave small gaps like sockets in.
- Plan the layout from the centre of the wall or room so cuts at both edges are the same size.
- For a bathroom, tile behind where the bath or basin panel meets the wall so there’s no gap to seal.
Questions people ask
How much extra tile should I order?
Ten per cent for a straight lay in a simple room. Allow 15% for diagonal or herringbone layouts, small rooms with lots of cuts, or large-format tiles where one broken tile is a big loss.
How much tile adhesive do I need per m²?
It depends on the trowel notch and the tile. Bags usually give a coverage table, often between about 2 and 6 kg per m². Type the figure from your bag into the calculator.
Should I count the grout joint?
Yes, for a precise count. Each tile covers its own size plus one joint. With large tiles it hardly matters, but with small mosaics or 5mm joints it can change the count by several per cent.
Can I buy one extra box later?
You can, but the colour or shade batch may not match. Buy everything at once, and keep a few spare tiles for future repairs.
Sources
This calculator only uses the measurements and figures you type in, so there are no outside figures to cite. The formula is shown above.
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Figures last checked 25 October 2026. Read how we calculate and our disclaimer. Found a mistake? Tell us.