Tile Calculator
Work out how many tiles you need for a floor or wall, including the grout joint, a waste allowance, whole boxes and total cost.
Area to tile
Tile & joint
Boxes & price (optional)
Fill in the room and tile sizes — the totals update as you type.
- Area to tile
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- Tiles needed
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- Tiles before waste
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- Extra for cuts
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- Tile + joint
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- Per tile
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- Boxes to buy
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- Total cost
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An estimate for planning and shopping, not a substitute for measuring the real room. Buy the full boxes in one batch so the shade codes match, and keep the spares for future repairs.
How it works
The calculator uses the grout-inclusive tile footprint method. Each tile really occupies its own size plus one grout joint on two of its sides, so a 30 × 30 cm tile with a 3 mm joint takes up 30.3 × 30.3 cm = 0.0918 m². Dividing the area you are tiling by that footprint gives the bare number of tiles: a 4 × 3 m room (12 m²) needs 12 ÷ 0.0918 = 130.7, so 131 whole tiles. The waste percentage is applied to the exact (unrounded) figure and the result is rounded up — at the default 10 % that is 130.7 × 1.1 = 143.8, so 144 tiles.
Waste covers the tiles you cut at walls, doorways and around pipes, plus the odd breakage. 10 % is the usual allowance for a straight or grid layout in a simple rectangular room; go to 15 % for a diagonal layout or many alcoves, and 20 % for herringbone and other angled patterns. Add a couple of spares on top for future repairs. Enter tiles per box and a price to see how many boxes to buy — always rounded up to whole boxes — and what the job costs.
Switch between metric and imperial at any time and the numbers you already typed are converted for you. You can also subtract an area that will not be tiled, such as a kitchen island footprint or a shower tray. Everything is computed in your browser in plain JavaScript: nothing is uploaded, there are no sign-ups and no ads.
Frequently asked questions
How do I calculate how many tiles I need?
Divide the area you are tiling by the area one tile actually occupies — its own size plus one grout joint on two of its sides. A 30 × 30 cm tile with a 3 mm joint takes up 30.3 × 30.3 cm = 0.0918 m², so a 4 × 3 m room (12 m²) needs 12 ÷ 0.0918 = 130.7, rounded up to 131 whole tiles for bare coverage. Add your waste allowance on top: at 10 % that is 130.7 × 1.1 = 143.8, so 144 tiles. This calculator applies the percentage to the exact unrounded figure and rounds up once at the end, which is the correct order and avoids over-buying.
How much extra should I add for cuts and breakages?
10 % is the standard allowance for a straight or grid layout in a simple rectangular room. Go to 15 % if you are laying on the diagonal, tiling a room with lots of alcoves, doorways or pipe cut-outs, or using large-format tiles where one bad cut wastes a big piece. Herringbone and other angled patterns usually need 20 %. Add a couple of spare tiles beyond that and store them: batches vary slightly in shade, so a repair years later will not match unless you kept some from the original run.
Does the grout joint really change the tile count?
Yes, and more than people expect on small tiles. Ignoring a 3 mm joint on a 30 cm tile overstates the count by about 2 %, but on a 10 cm mosaic-sized tile the same joint is roughly 6 % of each dimension and can add up to a whole extra box. This calculator always includes the joint in the tile footprint. Set the grout field to 0 if you are laying rectified tiles butt-jointed, and remember to buy in whole boxes — the boxes-to-buy figure here already rounds up for you.