Paint Calculator
Liters and cans of paint for the walls in the same room.
OpenTile Calculator
Calculate how many boxes of tiles you need for floors or walls — with waste included — for any rectangular surface.
What this calculates
Calculates the net area, area with waste allowance and total number of boxes needed to tile a rectangular surface.
Formula used
Area = length × width. Area with waste = area × (1 + waste %). Boxes = area with waste ÷ m² per box (rounded up).
Worked example
A room of 4 m × 3 m has 12 m². With 10% waste: 13.2 m². If each box covers 2 m², you need 7 boxes.
Typical waste allowances
Straight lay: 10%. Diagonal (45°): 15%. Rooms with many cuts or irregular shapes: 15–20%. Always buy extra boxes from the same production lot to match color and texture.
When not to use this calculator
For rooms with curved walls, multiple alcoves or complex patterns, increase the waste percentage manually. This calculator assumes a simple rectangular surface.
How to use this calculator
- Enter the length and width of the surface to tile in meters (or use the imperial toggle to enter in feet).
- Enter the m² per box — this is printed on the product label. Standard boxes typically cover 1.5–2.5 m².
- Set the waste factor — 10% for straight-lay, 15% for diagonal, 20% for complex patterns or many cuts.
- Optionally add a price per box to get a preliminary material cost.
- Click "Calculate tiles" to get the number of boxes, net area and area with waste instantly.
Tile installation methods and standards
The right installation method depends on the substrate, tile size, and intended use. Major standards that govern tile installation include:
- ANSI A108 / A118 (USA): Defines installation methods, adhesive types (thinset mortar, epoxy) and grout specifications for ceramic, porcelain and stone tile.
- BS 5385 / BS 8000-11 (UK): Wall and floor tiling standards covering substrate preparation, adhesive selection and grouting.
- ISO 13006 (International): Classifies ceramic tiles by water absorption and breaking strength — key for choosing between wall and floor tiles, and for wet or frost-exposed areas.
Key rules for a durable installation: the substrate must be flat (3 mm tolerance over 3 m), clean and dry. Tiles with water absorption below 0.5% (porcelain, group BIa) are fully vitrified and required for outdoor or heavily used indoor floors. For wet areas, a tanking membrane applied before tiling is mandatory — tile alone is not waterproof.
Grout and adhesive quantities
This calculator estimates tile boxes only. You will also need:
- Thinset adhesive (mortar): Typically 3–5 kg per m² for floor tiles, 2–4 kg/m² for wall tiles, depending on tile size and back-butter method. A 25 kg bag covers approximately 5–8 m².
- Grout: Depends on tile size and joint width. For a 30×30 cm tile with 3 mm joints, about 0.8 kg/m² of unsanded grout is typical.
- Tile spacers: Use 2–3 mm for rectified tiles, 3–5 mm for standard tiles. Always use spacers — eyeballed joints drift.
Frequently asked questions
How many tiles do I need per m²?
It depends on the tile size. Check the coverage per box on the product label and enter that value in the field above.
How much waste should I add?
10% for straight lay, 15% for diagonal. Add more for irregular rooms or many cuts.
How many m² are in a box?
Typically 1.5–2.5 m². Check the product label for the exact coverage per box.
Do I need adhesive?
Yes. Tile adhesive (thinset) and grout are needed. Coverage per bag varies — check the manufacturer specs.
How many tiles do I need for 100 square feet?
It depends on tile size. For 12×12 in tiles (1 sq ft each): 100 tiles + 10% waste = 110 tiles. For 18×18 in tiles (2.25 sq ft each): 45 tiles + 10% waste ≈ 50 tiles. For 24×24 in tiles (4 sq ft each): 25 tiles + 10% waste ≈ 28 tiles. This calculator works with box coverage in m² — enter your room area and the m²-per-box from the product label.
Should I buy extra tile for future repairs?
Yes. Always buy 10–15% more than you calculate, and keep the surplus. Tile production runs vary — if you need to replace a cracked tile in 5 years, matching the original lot is often impossible. Buying extra from the same batch is free insurance.
Assumptions
- Boxes are rounded up to the nearest whole box.
- Waste is applied to the net area.
- Does not include adhesive, grout or tile spacers.
- Valid for simple rectangular surfaces only.
Technical warning
Wet areas (showers, pool surrounds) require waterproofing membranes, suitable tile adhesives and proper grout. Always follow manufacturer specifications.
Common mistakes
- Buying tiles from different production lots (color mismatch).
- Not checking whether the surface is flat and plumb before tiling.
- Underestimating waste for diagonal or complex patterns.
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