Tile & Grout Calculator
Plan floor and wall tiling: work out how many tiles you need, including grout joints and a waste margin, and estimate the cost
Project Dimensions
Round up to full boxes when you buy. Different production batches can vary slightly in color, so buy everything at once.
How to use this tool
- Choose m² (Metric) or sq ft (US) and enter the project area.
- Enter the tile length and width, then pick the grout joint width.
- Choose a waste margin: 5–10% for simple rooms, 15% for diagonal layouts, 20% for herringbone.
- Optionally add the price per area unit, then read the number of tiles, the area including waste and the cost.
Worked example
For a 20 m² floor with 60 × 60 cm tiles, a 2 mm joint and 10% waste, each tile effectively occupies 0.602 × 0.602 = 0.3624 m². The tool needs 22 m² ÷ 0.3624 ≈ 60.7, rounded up to 61 tiles. If you lay the same tiles diagonally and choose 15% waste, the area becomes 23 m² and the count rises to 64 tiles. At a price of 25 per m², the tool shows 22 × 25 = 550, but boxes are sold whole, so ask the shop how many tiles each box holds and round up to complete boxes.
Methodology
Accurate tile estimation prevents delays from running short and money wasted on over-ordering by accounting for grout lines and breakage. The formula is tiles = round up of [area × (1 + waste)] / [(tile length + joint) × (tile width + joint)]. Worked example: 20 m² with 30 × 30 cm tiles, a 3 mm joint and 10% waste gives 22 m² / 0.0918 m² = 239.6, rounded up to 240 tiles.
Five ways a tile order goes wrong
Tile orders usually fail on small details, not on the main formula. Here are the slips that cost the most, and how the calculator handles each one.
- Ignoring the joint on small tiles. A 10 × 10 cm tile with a 3 mm joint really occupies 10.3 × 10.3 cm, 6% more area. For 10 m² that is 943 tiles, not 1,000. The tool always adds the joint, so set the joint width honestly.
- Using one waste figure for every layout. For 20 m² of 60 × 60 cm tiles with a 2 mm joint, 10% waste means 61 tiles, 15% (diagonal) means 64 and 20% (herringbone) means 67. Pick the margin that matches the pattern.
- Mixing up units. In metric mode tile size is in centimeters and the joint in millimeters; in US mode both are in inches. Typing 60 into an inch field describes a five-foot tile.
- Forgetting that tiles come in boxes. The result is a tile count, not a box count. If a box holds 4 tiles, 61 tiles means 16 boxes (64 tiles), so round up and ask the shop.
- Trusting the cost as a final price. It is the price per area unit times the area including waste: 20 m² at 25 with 20% waste is 600. Real boxes, delivery and offcuts will change it.
The tool does not subtract doors or fixtures and assumes a plain rectangular layout, so enter the net area you will actually tile.
Frequently asked questions
Why do I need a 10% waste margin? ▼
The 10% rule accounts for tiles that need to be cut to fit edges and corners, as well as accidental breakages during transit or installation. Without this margin, you risk running out of tiles before the job is finished.
Do diagonal or herringbone patterns need more tiles? ▼
Yes. Diagonal layouts create more corner cuts and off-cuts that cannot be reused. It is standard to order 15% extra for diagonal patterns, and up to 20% extra for complex herringbone or custom mosaic layouts.
Why is it important to buy all boxes at once? ▼
Ceramic and porcelain tiles are manufactured in batches (production runs). Even the exact same model can have slight color or caliber variations between batches. Ordering everything at once ensures visual consistency across the entire room.
How do I turn the tile count into boxes to order? ▼
Divide the tile count by the number of tiles per box printed on the packaging, then round up. If the calculator shows 240 tiles and a box holds 11, you need 240 / 11 = 21.8, so 22 boxes (242 tiles). Many suppliers sell by the box covering a stated area instead, so check whether the label lists tiles or square meters per box. Keep the spare tiles for future repairs, because the same model can be hard to match later. Large-format tiles and rectified edges are often laid with narrow joints, so enter the joint your installer will actually use.