Floor Tile Calculator — Area, Tiles, Adhesive & Grout
Calculate how many floor tiles you need for any room size, along with adhesive and grout quantities. Supports all tile sizes and lay patterns — straight, brick-bond and diagonal — with accurate waste factors for each.
How the floor tile calculator works
- 1Room area = length × width (m²), minus any fixed furniture footprints
- 2Tiles needed = area ÷ (tile length × tile width) × waste factor
- 3Waste: 10% straight lay, 15% brick bond, 17% diagonal lay
- 4Adhesive: area × coverage rate (3.5–5.5 kg/m² based on tile size)
- 5Grout: tile perimeter ÷ (tile area) × joint width × tile thickness × 1.7 kg/dm³
- 6Round up tiles to whole boxes; round adhesive and grout to nearest bag
Worked example
Open-plan living area: 5 m × 6 m = 30 m². Large format 600×600 mm tiles, straight lay (10% waste).
You need 92 tiles (0.36 m² each), 150 kg adhesive (5 kg/m² for large format) and approximately 5.5–6 kg grout at 3 mm joints (0.17 kg/m² × 30 m² + 10% waste).
Frequently asked questions
What size tiles make a room look bigger?
Larger tiles (600×600 mm or 800×800 mm) with narrow joints create fewer visual interruptions and make rooms appear more spacious. Lay them diagonally for further visual expansion — but budget for 17% waste.
Should floor tiles be laid straight or at an angle?
Straight lay is easiest and most economical (10% waste). Diagonal/45° lay adds visual interest but increases waste to 17% and requires cutting along all four walls. Brick bond is a popular compromise at 15% waste.
How thick should floor tile adhesive be?
Typically 3–6 mm bed thickness. Large format tiles require back-buttering to achieve full (≥80% in dry areas, ≥95% in wet areas) coverage. Thin-bed adhesive should not exceed 6 mm; use a levelling system for uneven substrates.
Can I tile over existing floor tiles?
Yes if: the existing tiles are firmly bonded (none hollow-sounding), the floor height increase is acceptable, and the subfloor can handle the additional load. Use a suitable primer and a C2 adhesive for bonding tile-on-tile.
What joint width for floor tiles?
2–3 mm for rectified large-format porcelain tiles. 3–5 mm for standard ceramic floor tiles. Never lay large-format tiles butted (no joint) — thermal expansion will cause debonding or cracking.