Tile quantities
Tiles per square metre including joint width
- where
- tiles per square metre
- tile length and width (mm)
- joint width (mm)
- area covered per tile including joint (m²)
Explain this equation
Tells you how many tiles cover one square metre once the grout joint is allowed for. It is the starting point for any tile order.
L and W are the tile length and width and j is the joint width, all in millimetres. Each tile, with one joint along one long side and one short side, forms a repeating block of (L + j) by (W + j). That block area, a, is what one tile really covers on the wall or floor.
One square metre is 1 000 000 mm², so dividing it by the block area gives tiles per square metre. The joint is added to both dimensions because the grid repeats every tile plus one joint in each direction.
Sense check: 300 × 300 mm tiles with no joint give 11.1 per m²; with a 3 mm joint it drops to about 10.9. For 600 × 300 mm with 2 mm joints it is about 5.5 per m².
Watch out: the joint makes a bigger difference on small tiles and wide joints. On mosaics and hexagons use their own calculators.
How many tiles cover one square metre once the grout joint is allowed for. Each tile plus one joint on two sides forms the repeating module.
Enter your values to see the result.
Good to know
BS 5385 sets minimum joints of about 2 mm on internal walls and 3 mm on floors; rectified porcelain is often laid at 2–3 mm, handmade and rustic tiles at 5 mm or more. The joint matters more on small tiles: on 100 × 100 mm with 3 mm joints, almost 6% of the surface is grout.
Common mistake
Dividing 1 m² by the tile face size alone. On small tiles and wide joints this overstates the tiles needed noticeably.
Limits
Rectangular tiles in a grid or bond. For hexagons and mosaics use their own calculators. This is a net figure with no cutting waste.
Sources
- Tile Mountain: How many tiles do I need? (wastage by pattern: straight 10%, brick bond 10–15%, diagonal 15%, herringbone 15%)
- BAL Flex One technical data sheet (coverage per notched trowel, 2–8 mm bed, 3 mm minimum on floors)
- NHBC Standards 9.3.5 Ceramic, concrete, terrazzo and similar tile finishes (solid bed, 3 mm joints, BS 5385-3/-4)
Results are calculations from the published methods and manufacturer figures shown, and depend on the data you enter. Always follow the tile, adhesive and grout manufacturers’ instructions, BS 5385 and the Tile Association guidance. Coverage rates vary by product and substrate. Check prices and VAT rules with your own records and HMRC.