About the Tile Calculator
Buying too few tiles is annoying and buying too many wastes money. This tile calculator takes your room length and width, the size of one tile, the width of the grout joint and an allowance for cuts and breakage, and works out how many tiles to buy. If you know how many tiles come in a box, it also gives the number of boxes and how many spare tiles you will have left. You can work in feet and inches or metres and centimetres. It divides the floor area by the area each tile takes up, including its share of the grout joint.
Updated October 2026
How to use the Tile Calculator
- 1Choose feet and inches, or metres and centimetres.
- 2Enter the room length and width.
- 3Enter the tile width and length, and the grout joint (use 0 to ignore it).
- 4Add a waste allowance, 10 percent for a simple layout, more for diagonal patterns.
- 5Enter tiles per box if you know it, then read the tile count and boxes.
Measuring the room
Measure the longest length and width of the area you will tile, using the same unit for both. Measure to the walls rather than to the skirting if the tiles will go underneath. If there are alcoves, add them as separate rectangles. Fixed items that tiles will not go under, such as a bath or kitchen units, can be left out of the area.
Choosing the waste allowance
- 5 to 10%: simple straight layout in a regular room
- 10 to 15%: larger tiles or rooms with many corners
- 15 to 20%: diagonal layouts, herringbone and patterned tile
- Plus a few spares for future repairs
Ordering tips
Buy all tiles from the same batch, since colour and size can differ slightly between production runs. Check the box for the batch or shade number. Keep unopened boxes if the supplier accepts returns. Remember that this tool estimates tiles; adhesive, grout and spacers are separate purchases and depend on the product you choose.
Related tools
The Area Calculator helps with unusual shapes, the Square Footage conversions in the Unit Converter help when the tile packaging uses different units, and the Paint Calculator, Concrete Calculator and Gravel Calculator cover other building materials. The Volume Calculator is useful for screed and adhesive depth.
Features
- Tiles needed, with and without waste
- Boxes to buy and spare tiles left over
- Grout joint taken into account
- Feet and inches or metres and centimetres
- Any rectangular tile size, including long planks
- Clear checks for impossible sizes
- Runs in your browser
Frequently asked questions
How do I calculate how many tiles I need?
Multiply the room length by the width to get the area, then divide by the area of one tile including its grout joint, and round up. A 10 by 12 foot room is 120 square feet, so it needs 120 tiles of 12 by 12 inches before waste. The calculator does this, then adds your waste allowance.
How much extra tile should I buy?
Ten percent extra is the usual allowance for a straight layout. Use 15 percent or more for diagonal layouts, herringbone patterns, small rooms with many cuts, or very large tiles. A few spare tiles are also useful for future repairs, because later batches may not match in colour.
Does the grout joint change the number of tiles?
Slightly. Each tile plus its joint takes up a bit more space than the tile alone, so wider joints mean fewer tiles. The effect is small for narrow joints and larger for small tiles such as mosaics. Enter your planned joint, or 0 to ignore it.
Can I use it for walls?
Yes. Enter the wall height as the length and the wall width as the width. For several walls, calculate each one and add the totals, or enter the combined area as one long strip. Subtract large windows and doors only if you are sure you will not tile around them.
What size are boxes of tiles?
It varies by product. A box may hold anywhere from 4 large tiles to dozens of small ones, and is usually labelled with the area it covers. Enter the number of tiles per box and the calculator rounds up to whole boxes.
Does it work for irregular or L-shaped rooms?
Split the room into rectangles, calculate each and add the results. Add a little extra waste, since more edges mean more cuts. For curved areas, measure the longest length and width and use a higher waste figure.