Tile Calculator
Work out how many tiles a floor or wall needs: enter the areas, the tile size and the grout joint, and get the tile count with waste added, the boxes to buy, the total area and a thinset estimate.
The waste allowance is already in the tile count, and boxes are whole — keep the spares, they are what makes a repair possible years later.
Formula and calculation
Worked example
Two areas, 12 × 14 ft and 8 × 10 ft, come to 248 sq ft of floor. With 12 in tiles and a 1/8 in joint each module covers about 1.02 sq ft, so the job needs 268 tiles with waste — buy 14 boxes of 20, which is 280 sq ft of tile. Allow 3 bags of thinset for the floor.
Where tile waste actually goes
Waste is not mostly breakage. Tiles are cut at the perimeter, so the last row is almost never a full tile, and inside corners, doorways and out-of-square walls eat more. A straight lay needs about 10%, a diagonal or offset lay 15%, and herringbone 20%. Keep one spare box in the garage: dye lots change between production runs, so a repair years from now will not match a fresh batch from the store.
Tile size, joints and substrate
Small tiles follow an uneven floor and need more grout lines; large-format tile wants a flat substrate and a bigger notch trowel, which uses more thinset. Use a 1/8 in joint for most ceramic and porcelain, 1/16 in for rectified edges, and 3/16–1/4 in for stone. On walls, check that the tile is rated for wall use — some natural stone and heavy porcelain need a cement backer board rather than drywall.
What the results mean
- Tiles to buy
- How many whole tiles the job needs, with the waste allowance already added and rounded up.
- Boxes
- The number of boxes to buy, rounded up — tile is sold by the box and you cannot buy half of one.
- Area
- The total area you entered, in square feet, added up across every line.
- Metric
- The same area in square meters, for metric tile sizes and product listings.
- Tile you will buy
- The tile face area the boxes you are buying actually contain — compare it with the area to see how much spare you end up with.
- Thinset mortar
- A rough count of 50 lb bags of thinset mortar for a 1/4 in × 1/4 in notched trowel, which most manufacturers rate at 85–95 sq ft per bag.
Frequently asked questions
How many tiles do I need for 100 square feet?
It depends on the tile size and the joint. With 12 in tiles and a 1/8 in joint each module covers about 1.02 sq ft, so 100 sq ft takes about 98 tiles, or 108 with a 10% waste allowance. Four-inch tiles cover only 0.118 sq ft each, so the same floor takes about 846 of them before waste.
How much extra tile should I buy?
10% for a straight lay, 15% for a diagonal or offset pattern and 20% for herringbone — that is what the waste box above does. Keep the leftovers: matching a discontinued tile later is close to impossible, and a spare box costs far less than retiling a room.
Should the grout joint be added to the tile size?
Yes, for a quantity takeoff. Tiles are set with a joint between them, so the distance that repeats across the floor is one tile plus one joint. Ignoring the joint over-orders by a few percent, which on a large floor is a whole extra box.
How much thinset do I need?
A 50 lb bag covers roughly 85–95 sq ft with a 1/4 in × 1/4 in notched trowel, the usual setup for tile up to 12 in. Large-format tile, back-buttering and uneven floors all use more, so treat the bag count as a starting point and buy one spare on a big job.