Tile Calculator
Count the tiles and boxes for a floor or wall, including grout joints, openings and layout waste for straight, diagonal or herringbone, plus grout weight.
The interactive tool loads here when JavaScript runs.
About this toolWhat is the Tile Calculator?
Tile is bought in whole boxes and fitted around corners, so the useful answer is never just "area divided by tile size". This tile calculator starts from the room, subtracts tubs, vanities and doorways, adds the grout joint to each tile so the spacing is counted, and then applies a waste allowance that depends on how you lay the pattern. The result is the number of tiles to buy and the number of boxes that holds them.
Tile size and joint width are entered in inches or millimetres, and the room in feet or metres. Choose a layout and the waste percentage is filled in for you: 10% for a straight grid, 12% for a brick offset, 15% for diagonal and 20% for herringbone. You can overwrite the figure for your own room. Boxes can be counted from tiles per box or from the coverage printed on the carton.
A grout estimate uses the formula adhesive manufacturers publish, so you can buy grout in the same trip. Prices per box give a material cost to compare tiles before you commit.
- Grout joint counted in every tile, not just the tile face
- Layout presets for straight, offset, diagonal and herringbone waste, all editable
- Boxes from tiles per box or coverage per box, with a cost estimate
- Grout weight in kg and lb from the published manufacturer formula
- Imperial and metric with automatic conversion; copy and share link
How to use the Tile Calculator
- Choose imperial or metric, then enter the room length and width, or switch to entering the area directly.
- Add the area of openings that will not be tiled, such as a tub, shower tray or kitchen cabinets.
- Enter the tile length, width and grout joint. In imperial, a 1/8 inch joint is 0.125.
- Choose the layout to set the waste preset, and adjust the percentage if your installer suggests a different figure.
- Enter tiles per box (or coverage per box) and a price to see the boxes and cost; add tile thickness for the grout estimate.
Worked examples
Bathroom floor with 12 in tiles
Input
12 x 10 ft, 12 x 12 in tile, 1/8 in joint, straight lay (10%), 10 tiles per box
Output
130 tiles (117.5 to cover exactly), 13 boxes, about 3.9 kg of grout at 3/8 in thick
This is the default example. Counting the joint lowers the exact figure from 120 to 117.5 tiles before waste.
Diagonal 600 x 300 mm tiles
Input
2.4 x 1.8 m, 600 x 300 mm tile, 3 mm joint, diagonal (15%), boxes cover 1.44 m²
Output
28 tiles, 4 boxes, about 1.2 kg of grout at 10 mm thick
At 23.6 tiles exactly, the 15% diagonal allowance adds four tiles. Since a box holds eight, four boxes leave a few spares.
Herringbone plank tile
Input
40 ft² area, 24 x 4 in planks, 1/16 in joint, herringbone (20%)
Output
71 tiles (58.9 exact)
Small planks in a herringbone pattern use the highest waste figure because every edge piece is an angled cut.
Background and insight
Each tile occupies its own size plus one joint in each direction. A 12 inch tile with a 1/8 inch joint takes up 12.125 x 12.125 inches, about 2% more than the tile, so a calculator that ignores joints overstates the count for large tiles and is close enough only for very small joints. The difference grows quickly with mosaic and small subway tiles, where the joint is a larger share of each piece.
Waste comes from cuts at the edges. A straight lay wastes mainly the offcuts along two walls. Diagonal and herringbone patterns cut nearly every edge piece at an angle, and the triangles left over are rarely reusable, so installers plan 15 to 20%. Large-format tiles also waste more because a single bad cut costs a big piece. Keep a few spare tiles after the job; matching the dye lot years later is often impossible.
The grout figure comes from (A + B) / (A x B) x C x D x density, with tile length A, width B, tile thickness C and joint width D in millimetres and a density around 1.6 kg per litre for cement grout. It gives kilograms per square metre of floor.
Common use cases
Bathroom and kitchen floors
Subtract the tub, vanity or cabinet footprint and get a box count to order before demolition starts.
Shower and backsplash walls
Enter each wall as a length by height, subtract the window or niche, and use a small tile with its real joint.
Comparing tile options
Change tile size and price per box to see how a larger format or different pattern changes the order and total cost.
Ordering grout with the tile
Use the grout weight to choose between a small and large bag so the job is not held up halfway.
Tips and limitations
- Buy all the tile from one batch and check the shade code on every box before you start.
- Round up to whole boxes. Returning one unopened box is easier than finding a matching one later.
- Lay out a dry row along the longest wall to see where cuts fall. Shifting the starting line can avoid thin slivers at a doorway.
- Wall tile around a window or niche wastes more than a plain wall, so add a few percent beyond the layout preset.
- Grout weight varies with product and joint depth. Treat the estimate as a guide and check the coverage chart on the bag.
Frequently asked questions
How many tiles do I need for a 10 x 12 room?
With 12 inch square tiles and a 1/8 inch joint, the 120 ft² floor needs 117.5 tiles to cover exactly. Adding 10% for a straight lay gives 130 tiles, or 13 boxes of 10.
How much extra tile should I buy for a diagonal or herringbone layout?
Plan about 15% extra for a diagonal lay and 15 to 20% for herringbone, compared with 10% for a straight grid. The angled cuts at every wall leave triangles that rarely fit anywhere else.
Does grout joint width change how many tiles I need?
Yes, slightly. Each tile covers its own size plus one joint each way, so wider joints mean fewer tiles. For 12 inch tiles a 1/8 inch joint saves about 2%; for small mosaics the effect is much bigger.
How do I work out how many boxes of tile to buy?
Divide the number of tiles (with waste) by the tiles per box and round up. If the carton only lists square footage, divide the area you need by the box coverage instead and round up.
How much grout do I need per square metre?
Use (A + B) / (A x B) x C x D x 1.6, with tile length and width, tile thickness and joint width in millimetres. For 300 x 300 mm tiles, 8 mm thick, with 3 mm joints, that is about 0.26 kg per square metre.
Should I subtract the area under a bathtub or cabinets?
Usually yes. Tile is rarely laid under a built-in tub, vanity or kitchen base cabinets, so subtract their footprint. Leave it in if the floor runs underneath, for example under a freestanding tub.
Is there an in-depth guide to the Tile Calculator?
Yes. “Estimating Concrete, Flooring, Tile and Gravel Without Running Short” covers the background, how it works, common pitfalls and worked examples. Read the full guide.
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