About Tile Calculator (Tiles, Thinset & Grout)
The tile calculator counts the tiles, thinset, and grout to buy for a floor or wall. Enter the area directly or as length × width, then the tile size, grout joint width, tile thickness, lay pattern, and tiles per box. Each tile occupies its own footprint plus a share of the surrounding joint, so the effective coverage of one tile is (width + joint) × (length + joint), and the count is grossed up by a pattern waste allowance — 10% for a straight or offset (running bond) lay, 15% on the diagonal, and 20% for herringbone, where every course is cut at the walls.
Thinset mortar is counted in 50-lb bags from representative manufacturer mid-range coverage for the selected square-notch trowel: about 95 ft² per bag with a 1/4-inch notch, 65 ft² with 3/8 inch, and 45 ft² with 1/2 inch. Grout comes from the industry-standard joint-geometry formula — joint volume per square metre from the tile sides, joint width, and joint depth, times a 1.6 kg/dm³ bulk density factor — converted to pounds per square foot and rounded up into 10-lb and 25-lb bags. Both rates are representative and real products vary, so confirm against the coverage chart on the bag you buy.
How It Works
- Enter the area to tile directly in square feet, or switch to length × width mode and enter the two dimensions in feet (up to 50,000 ft²).
- Enter the tile width and length in inches (0.5 to 48 in, presets for 12×12, 6×24 plank, 3×6 subway, and 24×24), the grout joint width (0 to 1 in; 0 is a butt-set lay), and the tile thickness (0.1 to 1 in), which sets the grout joint depth.
- Pick the lay pattern — straight, offset/running bond, diagonal, or herringbone — to set the waste allowance, and enter the tiles per box printed on the carton to convert the tile count into boxes.
- Pick the square-notch trowel (1/4, 3/8, or 1/2 in) the thinset will be combed with; larger tile needs a deeper notch and therefore more mortar per square foot.
- Read the results: tiles and boxes to buy, 50-lb thinset bags, grout demand in lb/ft² and total pounds with 10-lb and 25-lb bag counts, and a chart comparing the tile count across all four patterns at your inputs.
Worked Example
A 100 ft² bathroom floor gets 12×12 in porcelain, 3/8 in thick, with a 1/4 in joint, laid straight, sold 10 tiles to a box, set with a 1/4-inch square-notch trowel. Each tile covers (12 + 0.25)² / 144 = 1.0421 ft² including its joint share, so the net count is 100 / 1.0421 = 95.96 tiles, and with 10% straight-lay waste that grosses up to ceil(105.56) = 106 tiles — 11 boxes of 10. Thinset at 95 ft² per 50-lb bag needs ceil(100 / 95) = 2 bags. For grout, the joint geometry in metric is A = B = 304.8 mm, C = 6.35 mm, D = 9.525 mm, giving (609.6 / 92,903.04) × 6.35 × 9.525 × 1.6 = 0.635 kg/m² = 0.130 lb/ft², or 13.0 lb over the floor — two 10-lb bags or a single 25-lb bag.
Formulas
- Effective tile footprint
A_tile = (W + j) x (L + j) / 144- Tiles and boxes to buy
N = ceil( A / A_tile x (1 + w) ); boxes = ceil( N / n_box )- Thinset bags
bags = ceil( A / coverage_trowel )- Grout demand (joint geometry)
kg/m² = ((A + B) / (A x B)) x C x D x 1.6- Grout in US units
lb/ft² = kg/m² x 0.204816; total lb = lb/ft² x A; bags = ceil(total / 10) or ceil(total / 25)
Standards & References
- ANSI A108 series — installation of ceramic tile (setting practice)
- ANSI A118.1/A118.4 — dry-set and modified dry-set cement mortar specs
- ANSI A118.6/A118.7 — standard and high-performance cement grout specs
- TCNA Handbook — method selection and coverage guidance (advisory)
Frequently Asked Questions
How much extra tile should I buy for waste?
It depends on the lay pattern. A straight grid or offset (running bond) lay typically wastes about 10% to cuts, breakage, and future repairs. A diagonal lay cuts every perimeter tile at 45°, pushing waste to about 15%, and herringbone — where courses run at an angle and every wall row is cut — commonly needs 20%. The calculator applies these factors automatically; small or oddly shaped rooms with many penetrations sit at the high end.
Why does the grout joint width change the tile count?
Each tile effectively covers its own face plus half the joint on all four sides, which works out to (width + joint) × (length + joint). With a 12×12 tile and a 1/4-in joint that is 1.042 ft² per tile instead of 1.0 ft², about 4% fewer tiles over a large floor. A zero joint (butt-set, common with rectified tile) makes the effective footprint exactly the tile face.
How much thinset do I need per square foot?
Coverage is set by the trowel notch, which is in turn set by the tile size. As representative mid-range manufacturer figures, a 50-lb bag combed with a 1/4-in square notch covers about 95 ft², a 3/8-in notch about 65 ft², and a 1/2-in notch (large-format tile) about 45 ft². Real coverage varies with the product, substrate flatness, and back-buttering, so treat the bag count as a buying estimate and check the coverage chart printed on the bag.
How is the grout quantity calculated?
From the joint geometry, using the industry-standard formula grout manufacturers print on their charts: kg/m² = ((A + B) / (A × B)) × C × D × 1.6, where A and B are the tile sides in millimetres, C is the joint width, D is the joint depth (taken as the tile thickness), and 1.6 kg/dm³ is a representative bulk density of mixed grout. The tool converts your inch inputs to millimetres, then reports lb/ft² and total pounds with 10-lb and 25-lb bag round-ups.
What grout joint width should I use?
Common practice is 1/16 to 1/8 in for rectified tile, 1/8 to 3/16 in for standard pressed porcelain and ceramic, and 3/16 to 1/4 in for handmade, natural stone, or tile with significant size variation. ANSI A108.02 practice also keys the minimum joint to the tile facial variation, and unsanded grout is generally limited to joints of 1/8 in or less while sanded grout handles wider joints.
Do wall tile and floor tile count differently?
The arithmetic is identical — the calculator works for either as long as you enter the area of the surface being tiled. What changes is the supporting detail: wall installations usually use smaller tile and narrower joints (a 3×6 subway with a 1/16-in joint is a preset here), thinset coverage is often better on flat walls, and the pattern waste factors still apply because perimeter cuts happen at ceilings, corners, and trim the same way they do at walls on a floor.