Work out how many tiles and boxes a floor or wall needs, including the grout joint width, a waste allowance based on the layout pattern, and estimates for thinset and grout.
Waste depends on the pattern, not on how careful you are. Straight lay needs about 10%; diagonal and large-format layouts need 15–20% because every edge cut produces an offcut that cannot be reused.
A 12×12 tile does not cover exactly one square foot once it is set with a joint. With a ⅛ inch joint the effective coverage is 12.125 × 12.125 inches, or 1.021 square feet, so a 100 square foot floor needs 98 tiles rather than 100. It sounds trivial, and it is, until you are tiling 1,200 square feet and the joint accounts for 25 tiles.
In a 200 square foot room with 12×12 tiles and ⅛ inch joints, the grout lines take up roughly 2% of the surface. That is why this calculator adds the joint to the tile dimensions rather than ignoring it.
| Layout | Waste | Why |
|---|---|---|
| Straight / stacked (grid) | 10% | Edge cuts only; the fewest cuts and the most reusable offcuts |
| Running bond (brick / subway) | 12% | Every other row is offset, so both ends of every row need a cut |
| Diagonal (45°) | 15% | Every tile meeting a wall is cut at an angle, producing triangular offcuts |
| Herringbone | 20% | Angled cuts in every row, and the offcuts are rarely reusable |
| Large format (24 in and up) | 20% | A single cut wastes a lot of material, and any breakage is expensive |
Add another 5% for bathrooms, showers and outdoor areas, where cuts around fixtures, drains and corners multiply quickly.
| Tile size | Area per tile | Tiles per 100 sq ft |
|---|---|---|
| 4 × 4 in | 0.111 sq ft | 900 |
| 6 × 6 in | 0.25 sq ft | 400 |
| 12 × 12 in | 1.0 sq ft | 100 |
| 12 × 24 in | 2.0 sq ft | 50 |
| 18 × 18 in | 2.25 sq ft | 45 |
| 24 × 24 in | 4.0 sq ft | 25 |
Large-format tiles mean far fewer pieces but need a flatter substrate and a bigger notched trowel, which uses more adhesive per square foot.
| Material | Typical coverage | Notes |
|---|---|---|
| Thinset, ¼ × ⅜ in notched trowel | ~50 sq ft per 50 lb bag | Standard for floor tile |
| Thinset, ½ × ½ in notched trowel | ~40 sq ft per 50 lb bag | Required for large-format tile; back-butter as well |
| Sanded grout, 25 lb bag | ~100 sq ft with 12×12 tile and ⅛ in joints | Use for joints ⅛ in and wider |
| Unsanded grout | Less coverage, small joints only | For glass, polished marble and joints under ⅛ in |
Grout consumption rises sharply with smaller tiles or wider joints, because there is more joint per square foot. A mosaic with 3 mm joints can use two to three times as much grout per square foot as a 12×12 tile.
The waste percentages by layout follow the guidance published by the Tile Council of North America and repeated in tile manufacturers' installation literature. Thinset and grout coverage figures are the standard trowel-and-bag estimates published by adhesive manufacturers; actual coverage varies with tile size, joint width and how flat the substrate is. Always check the manufacturer's coverage chart on the bag before you buy.
With 12×12 tiles, 100 tiles cover 100 square feet before any allowance, so order about 110 to cover 10% straight-lay waste. With a ⅛ inch grout joint each tile effectively covers 1.021 square feet, so the raw count drops to 98 and the order lands around 108.
10% for a straight grid in a simple room, 12% for a running-bond or subway layout, 15% for a diagonal pattern, and 20% for herringbone or large-format tile. Add another 5% in bathrooms and showers, where cuts around fixtures multiply.
Divide the tile count including waste by the coverage per box, then round up to the next whole box. Never round down: a single extra box costs far less than a second delivery or a shade mismatch from a different production batch.
Slightly. Adding the joint width to both tile dimensions accounts for it properly. In a 200 square foot room with 12×12 tiles and ⅛ inch joints the grout occupies roughly 2% of the surface, which is small but not nothing on a large job.
A 50 lb bag of thinset covers roughly 50 square feet with a ¼ × ⅜ inch trowel, dropping to about 40 square feet with the ½ × ½ inch trowel used for large-format tile. A 25 lb bag of sanded grout covers roughly 100 square feet with 12×12 tile and ⅛ inch joints.