Tile Calculator
Tiles = area × 1.10 ÷ the area of one tile with its joint (× 1.15 laid diagonally). A 12 × 10 ft floor in 12 × 24 in tiles with 1/8 in joints takes 65 tiles: 9 boxes of 8. Buy all the boxes from one production run (dye lot): Florida Tile notes that shades can vary between runs.
Tiles to buy
65 tiles
9 boxes of 8 · 132 ft² with 10 % extra
- Area to tile
- 120 ft² (11.15 m²)
- Tiles without the extra
- 60
- Grout (cement, sanded)
- 6.4 lb (2.9 kg)
- 25 lb bags of grout
- 1
- One 25 lb bag covers
- 471 ft²
Buy every box from the same lot (shade) number, and keep the spare tiles for later repairs.
Worked examples
A 12 × 10 ft floor in 12 × 24 in tiles, 1/8 in joints
- 12 × 10 = 120 ft² = 17,280 in²
- One tile with its joint: 12.125 × 24.125 = 292.5 in²
- 17,280 × 1.10 ÷ 292.5 = 64.98, so 65 tiles; 65 ÷ 8 = 8.1, so 9 boxes
Result: 65 tiles (68 laid diagonally), 9 boxes of 8.
Checked by the automated test “tile — 12 × 10 ft floor in 12 × 24 in tiles → 65 tiles with 10 %, 9 boxes of 8; 68 tiles diagonal”.
Grout for the same floor, tiles 3/8 in thick
- Per ft²: 144 × 0.125 × 0.375 × 36.125 ÷ 292.5 = 0.834 in³ of joint
- × 120 ft² = 100 in³ = 0.058 ft³
- × 110 lb/ft³ = 6.4 lb: one 25 lb bag
Result: 6.4 lb of grout, one 25 lb bag.
Checked by the automated test “tile — the same floor takes 6.4 lb of grout at 1/8 in joints: one 25 lb bag”.
How it works
Tiles = area (in²) × (1 + extra %) ÷ ((tile length + joint) × (tile width + joint)), rounded up
Boxes = tiles ÷ tiles per box, rounded up
Grout (in³) = area (in²) × joint × tile thickness × (length + width + joint) ÷ ((length + joint) × (width + joint))
Grout (lb) = grout (in³) ÷ 1,728 × 110 lb/ft³
Assumptions
- Extra tile: 10 % for a straight or offset layout, 15 % for diagonal or herringbone, Florida Tile's ordering rule; Florida Tile suggests 12 to 15 % for rooms with many cuts or tiles 24 × 24 in and larger, so pick the 15 % layout there.
- Grout at 110 lb/ft³: with it, the formula lands within 2.5 % of CUSTOM's Polyblend Plus coverage chart for tiles of 4 in and more, and on smaller mosaics it mostly asks for more grout than the chart.
- Cement grout, no waste added to the grout. For epoxy or premixed grout, use the maker's own chart.
Reference table
| Tile (in, thickness last) | Tiles per 100 ft², 1/8 in joint | 25 lb bag, 1/8 in joint | 25 lb bag, 1/4 in joint |
|---|---|---|---|
| 3 × 6 × 1/4 | 753 | 183 ft² | 96 ft² |
| 6 × 24 × 3/8 | 98 | 285 ft² | 146 ft² |
| 12 × 12 × 3/8 | 98 | 355 ft² | 180 ft² |
| 12 × 24 × 3/8 | 50 | 471 ft² | 238 ft² |
| 24 × 24 × 3/8 | 25 | 704 ft² | 355 ft² |
No extra included. CUSTOM's chart lists 348 ft² per 25 lb bag for 12 × 12 × 3/8 in tiles at 1/8 in.
Before you buy
- Walls too. Enter each wall as its own area (width × height), without the window and door openings.
- Tiles per box. Use the count printed on the box; if it gives ft² instead, divide by the area of one tile.
- Grout bag size. The result counts 25 lb bags; CUSTOM also sells Polyblend Plus in 7 lb bags for small jobs.
Common mistakes
- Too little extra on a diagonal A diagonal or herringbone layout cuts more tiles along the walls: Florida Tile raises the extra from 10 % to 15 %, 68 tiles instead of 65 here.
- Estimating grout from the area alone Grout follows the joint and the tile size: a 25 lb bag covers 471 ft² of 12 × 24 in tiles at 1/8 in, but 238 ft² at 1/4 in.
- Keeping no spare tiles Florida Tile's 10 % covers cuts, breakage and future repairs: keep the leftover tiles for the day one cracks.
Frequently asked questions
How do I figure out square feet for tile?
Split the room into rectangles, multiply length by width in feet and add them up. A 12 × 10 ft room plus a 5 × 8 ft closet is 160 ft²: enter both areas in the calculator.
How much tile will I need?
Area × 1.10 (1.15 for a diagonal layout) ÷ the area of one tile with its joint. For 120 ft² of 12 × 24 in tiles: 65 tiles, or 68 on the diagonal.
How much grout will I need?
It depends on joint width, tile size and thickness: 120 ft² of 12 × 24 × 3/8 in tiles takes 6.4 lb at 1/8 in joints and 12.6 lb at 1/4 in.
How much grout per square foot?
About 0.07 lb for 12 × 12 × 3/8 in tiles with 1/8 in joints, where CUSTOM's chart gives 348 ft² per 25 lb bag. For 1 × 1 in mosaics with 1/2 in joints, the chart drops to 24 ft² per bag, about 1 lb per ft².
Sources
Formula, examples and sources checked on by the Yardstick Math team. How we check our formulas.
- Polyblend Plus Sanded Grout – coverage chart, 25 lb and 7 lb bags — CUSTOM Building Products, accessed
- Tile ordering FAQ (10 % extra, 15 % for diagonal or herringbone) — Florida Tile, accessed
- Handbook 44, Appendix C – General Tables of Units of Measurement (1 ft² = 144 in², 1 ft³ = 1,728 in³) — NIST, accessed