Calculate tiles, boxes, grout, thinset, and total cost — with a live pattern preview.
| Room | Area | Base Tiles | +Waste | Total | Boxes |
|---|
Ordering too few tiles is a genuine disaster. Tile dye lots change between production runs — sometimes by a shade, sometimes significantly — and if you run short and need to reorder, you may end up with a noticeable color mismatch in the middle of your floor or shower wall. Ordering too many costs money and creates storage problems. The goal is a precise estimate with a calibrated waste buffer, and the math is straightforward once you understand every component.
Measure the length and width of each surface to be tiled in feet. Multiply them together to get square footage. For rooms with complex shapes — L-shapes, alcoves, closets — break the room into rectangles and sum the parts. This is your gross area. Do not subtract fixtures like toilets or bathtubs yet — tile is still installed underneath most permanent fixtures, and you need coverage to the walls behind them.
For walls, measure the height from floor to the desired tile height, then multiply by the wall width. For a shower with three tiled walls, calculate each wall individually. Note that window openings, niches, and doors are the only legitimate subtractions — and even then, only subtract if the opening is large enough that a complete tile won't be cut to fit around it (typically 10 square feet or more).
Convert your tile dimensions to feet (divide inches by 12), then multiply to get tile coverage area. A 12×12 inch tile covers exactly 1 square foot. A 6×6 tile covers 0.25 square feet. An 18×18 tile covers 2.25 square feet. Divide your total area by the tile coverage area to get the base tile count. Always round up — you cannot install a fraction of a tile.
Grout joints slightly reduce the effective tile coverage area. A 1/8-inch grout joint on a 12×12 tile means each "effective unit" (tile plus half the grout joint on each side) is actually 12.125×12.125 inches. This effect is negligible for large tiles but meaningful for small mosaic or subway tiles where grout joints represent a larger percentage of the tile face. This calculator accounts for grout joint width automatically.
The waste factor is not optional padding — it's a precise accounting for cut tiles, broken tiles, defective tiles rejected at the point of installation, and future repairs. The industry standard waste factor by layout pattern is: straight (grid) layouts use 10%, brick offset layouts use 10%, diagonal 45° layouts use 15%, and herringbone layouts use 15%. More complex patterns like Versailles or pinwheel use 20–25%.
Diagonal patterns require more waste because tiles must be cut at 45-degree angles along all four edges of the room, and each triangular cut piece produces a significant amount of unusable tile. A 24×24 tile cut diagonally at a room edge yields a triangular piece that cannot be repurposed elsewhere on the same edge. For small rooms where the perimeter-to-area ratio is high (like a 5×5 shower floor), increase your waste factor by 5% beyond the standard recommendation.
| Tile Size | Tiles per Sq Ft | Coverage (sq ft/tile) | Standard Waste | Diagonal Waste |
|---|---|---|---|---|
| 3×6" (subway) | 8.0 | 0.125 | 10% | 15% |
| 4×4" | 9.0 | 0.111 | 10% | 15% |
| 6×6" | 4.0 | 0.25 | 10% | 15% |
| 12×12" | 1.0 | 1.00 | 10% | 15% |
| 12×24" | 0.5 | 2.00 | 10% | 15% |
| 18×18" | 0.44 | 2.25 | 10% | 15% |
| 24×24" | 0.25 | 4.00 | 10% | 15% |
| 24×48" (large format) | 0.125 | 8.00 | 10% | N/A |
Tiles are sold in boxes of a specific quantity. Divide your total tile count (after waste) by the tiles-per-box number and round up to the next whole box. Never round down — buying one fewer box than needed triggers all the dye lot problems described above. The tiles-per-box number is always on the product label. Common pack sizes are 4 tiles (for large format 24×24 or 24×48), 12 tiles (for standard 12×12), 15–20 tiles (for 18×18), and 60–100+ tiles for mosaic sheets.
Grout joint width is both aesthetic and functional. Rectified tiles — cut to precise dimensions in a factory — can be installed with very tight 1/16-inch joints that nearly disappear. Non-rectified tiles have slight size variations from the kiln and require at least 1/8-inch joints to accommodate the dimensional inconsistency. Using joints that are too tight on non-rectified tile causes a wavy, uneven appearance as each tile pushes slightly against its neighbors.
Larger grout joints (1/4 inch and above) are typical for natural stone, hand-made tiles, large-format exterior pavers, and rustic or farmhouse aesthetics. Joints under 1/8 inch use unsanded grout, which has a smooth texture that won't scratch delicate tile surfaces like polished marble or glass. Joints 1/8 inch and wider use sanded grout, which is stronger and resists cracking in wider applications. Never use sanded grout on polished marble, glass tile, or any surface that scratches — the quartz aggregate in sanded grout will damage the finish permanently.
The tile itself is usually only 40–60% of the total material cost of a tiling project. Thinset mortar, grout, backer board, waterproofing membrane, spacers, and grout sealer add up quickly. Understanding what each material does — and calculating how much you need — prevents frustrating mid-project trips to the hardware store.
Thinset mortar (also called tile adhesive or tile mortar) bonds the tile to the substrate. Standard gray thinset works for most floor and wall applications. White thinset is used under light-colored grout or translucent tiles where gray bleed-through would affect the final color. Large-format tiles (18×18 and larger) require medium-bed mortar — a thicker, modified thinset that supports the extra weight without slumping and provides coverage to the full back of the tile.
Coverage rates vary significantly by trowel notch size, which is determined by tile size. Small tiles (under 8 inches) use a 3/16-inch V-notch or 1/4-inch square-notch trowel covering approximately 55 square feet per 50-pound bag. Standard floor tiles (8–16 inches) use a 1/4×3/8-inch notch covering 40–50 square feet per bag. Large format tiles use a 1/2-inch square-notch covering only 30–40 square feet per bag. Exterior and large-scale installations should add a "back-butter" coat to each tile, roughly doubling the thinset consumption.
Grout quantity is calculated using the standard tile industry formula: weight in pounds equals the sum of tile length and width (in inches) divided by the product of tile length and width, multiplied by the grout joint width, tile depth, 144, and the area in square feet, multiplied by a density factor of 1.65. For practical purposes: a 12×12 floor with 1/8-inch joints needs approximately 1 pound of grout per 20 square feet. The same floor with 1/4-inch joints needs 1 pound per 10 square feet.
Grout comes in two fundamental types: sanded (for joints 1/8 inch and wider) and unsanded (for joints narrower than 1/8 inch). Epoxy grout — a premium option used in commercial kitchens, laboratories, and pools — is far more stain-resistant and chemically inert than cement-based grout, but it is significantly more expensive, harder to work with, and sets very quickly. For residential shower floors, bathroom floors, and kitchen backsplashes, a high-quality sanded cement grout with grout sealer applied every 1–2 years is the standard approach. The grout color you choose will dramatically affect the overall aesthetic — light grout reads as clean and open, dark grout hides dirt and creates contrast.
Tile spacers are small plastic crosses or T-shapes that maintain consistent joint width during installation before the thinset cures. You'll need approximately 4 spacers per tile — one at each corner — though this is a rough estimate because spacers are shared between adjacent tiles. In practice, purchase spacers in bulk packs of 500–1,000 for any floor project. They cost $5–$15 per bag and are removed after the thinset sets (about 24 hours) before grouting. Do not leave plastic spacers in the joint and grout over them — they'll create voids and weaken the grout line.
Cement-based grout is porous. Without sealer, it absorbs water, cooking grease, soap scum, and mold spores. A quality penetrating grout sealer soaks into the grout's pores and creates a water-resistant barrier without affecting the appearance. Sealer coverage is typically 75–100 square feet per quart. Apply sealer 72 hours after grouting (fully cured), then annually for floor grout and every 6 months for shower grout. Epoxy grout does not require sealing.
| Material | Coverage per Bag/Unit | Used For | Typical Cost |
|---|---|---|---|
| Standard gray thinset (50 lb) | 40–55 sq ft | Standard floor/wall tile | $15–$25/bag |
| Medium-bed mortar (50 lb) | 30–40 sq ft | 18"+ large format tile | $25–$40/bag |
| Unsanded grout (25 lb) | 100–150 sq ft | Joints under 1/8" | $18–$35/bag |
| Sanded grout (50 lb) | 80–120 sq ft | Joints 1/8" and wider | $20–$40/bag |
| Epoxy grout (2-part kit) | 20–40 sq ft | Chemical resistance, pools | $50–$90/kit |
| Grout sealer (1 qt) | 75–100 sq ft | Cement grout protection | $12–$20/qt |
| Tile spacers (bag of 500) | ~125 tiles | All layouts | $5–$10/bag |
Tile cannot be installed directly on standard drywall in wet areas. Showers, bathtub surrounds, and areas subject to water splash require a cement backer board (like Hardiebacker or Durock) or a liquid waterproofing membrane applied over the substrate. Cement backer board is sold in 3×5-foot sheets and covers 15 square feet per sheet. Calculate backer board area the same way you calculate tile area. In wet areas, also apply a liquid waterproofing membrane at all seams, corners, and the shower floor before tiling.