Tile Calculator — How Many Tiles, Grout & Thinset Do I Need?

Divide your net floor area (in square feet) by the area of one tile, then add a waste factor: 10% for a straight layout, 15% for diagonal or herringbone. Example: an 8×10 ft bathroom = 80 sq ft; with 12×12 in tiles (1 sq ft each) and 10% waste you need ceil(80 × 1.10) = 88 tiles. This calculator does the math for you, including multi-room projects and openings like tubs or islands.

Use 10% for a simple straight layout in a rectangular room, 15% for diagonal or herringbone patterns, and 15–20% for rooms with many cuts, columns, or angled walls. The waste covers broken tiles, miscuts, and the fact that a cut-off piece usually cannot be reused. Our layout optimizer compares all three patterns side by side with their recommended waste factors.

Herringbone needs about 15% waste versus 10% for a straight layout, so roughly 5% more tile for the same area. The extra waste comes from the many angled cuts at walls and edges. For 80 sq ft with 12×12 tiles: straight needs 88 tiles, herringbone needs 92. Subway 3×6 herringbone on a 40 sq ft backsplash needs 368 tiles with 15% waste.

It depends on tile size and joint width. The formula is: grout (lb) = joint length per sq ft × joint width × joint depth × 0.058 lb/in³. As a rule of thumb, 80 sq ft of 12×12 in tile with 1/8 in joints and 1/4 in depth needs about 3.5 lb of grout (one small bag). The same area in 2×2 in mosaic needs about 21 lb — small tiles have far more joint length per square foot.

Grout weight = (joint length per sq ft) × (joint width) × (joint depth) × 0.058 lb/in³. Joint length per sq ft = 144 × (tile width + tile length) / (tile width × tile length) in inches — each joint is shared by two tiles, so each tile contributes half its perimeter. Joint depth is typically 2/3 of tile thickness. The calculator uses this formula, then rounds up to whole bags (10 or 25 lb).

Divide your square footage by the coverage per bag for your trowel notch. A 50 lb bag of thinset covers roughly 100 sq ft with a 3/16″ V-notch, 75 sq ft with 1/4″ × 1/4″, 50 sq ft with 1/4″ × 3/8″ (most floor tile), and 40 sq ft with 1/2″ × 1/2″ for large format tile. Example: 80 sq ft at 50 sq ft/bag = 2 bags. Back-buttering large tiles adds roughly 20%.

Plan on about one spacer per tile. The calculator estimates it from your room grid: tiles that fit across × tiles that fit down (for example a 9×11 grid = 99 spacers, buy a 100-pack). Cross spacers suit walls and straight floor layouts; T-spacers are handy where tile meets a wall or an offset (brick/subway) pattern.

Use the same area formula but raise the waste factor from 10% to 15% — diagonal layouts produce triangular offcuts at every wall, and those triangles are rarely reusable. Also budget extra time: diagonal and herringbone layouts are slower to set. The calculator's layout optimizer shows straight vs diagonal vs herringbone tile counts side by side for your exact area.

Divide tiles needed (with waste) by tiles per box and round up. Common box sizes: 12×12 in → 12 tiles/box (~12 sq ft), 24×24 in → 4 tiles/box (~16 sq ft), subway 3×6 in → ~80 tiles/box (~10 sq ft), 12×12 mosaic sheets → 10 sheets/box. Example: 88 tiles ÷ 12 per box = 7.33 → buy 8 boxes. The box optimizer does this for every tile size in the presets.

Measure length × width for the gross area, then subtract each fixture as its own rectangle (tub 3×5 ft = 15 sq ft, island 4×2 ft = 8 sq ft). In multi-room mode you can add each room with its own openings and the calculator sums the net area. Example: 8×10 ft bathroom minus a 3×5 ft tub = 65 sq ft → 72 tiles with 10% waste.

Check the leftover strip along each wall: remainder = room dimension mod (tile + joint). Avoid slivers under about 2 in (half a tile is the comfortable minimum) — if the remainder is tiny, shift the layout so cuts are balanced on both sides, or cut the first row. The min-cut estimator reports the exact leftover strip for your room and tile size.

Trim covers exposed tile edges: shower niches, pony walls, window returns, and the top row of a backsplash. A practical estimate is the perimeter of the tiled area — for an 8×10 ft room that is 36 linear ft → five 8-ft bullnose pieces (40 ft). For floors meeting a wall, baseboard covers the edge and no trim is needed. Adjust the exposed-edge percentage in the calculator for your project.

Yes. Switch to metric and enter rooms in meters and custom tile sizes in centimeters. All presets show metric equivalents (e.g. 12×12 in = 30×30 cm). Internally everything converts to square feet for the material formulas, then results display in m² and cm. Example: a 4×3 m room (12 m²) with 30×30 cm tile and 10% waste needs 147 tiles.

Add up: tile (boxes × price per box), grout bags, thinset bags, spacers, trim pieces, and any rental tools. The cost estimator multiplies your per-unit prices by the calculated quantities. Remember materials are only part of the job — professional installation labor in the US typically runs $5–$15 per sq ft on top of materials.

Yes — keep at least one full spare box (or 5% extra) after installation for future repairs. Tile dye lots change between production runs, so a tile bought later will never match perfectly. This is on top of the 10–15% installation waste, not instead of it.

Completely. This tool runs 100% in your browser — your room dimensions, prices, and results never leave your device. There are no accounts, no tracking of your inputs, and no server receiving your project data.