Estimate how many tiles — and optional boxes — you need to cover a floor, wall, roof, or other surface. Enter tile size, the area (or length and width), and the grout gap or overlap. Results include a 5–10% extra for cuts and waste, plus an optional material-cost estimate.
Use Planner to combine up to three floor or wall areas, subtract a cutout, record a straight or diagonal layout, apply your own waste allowance, round boxes, and add adhesive and grout from entered manufacturer coverage.
Tile layout and purchasing planner
Planner separates geometric need from the rounded order:
geometric tiles = ceil(net area ÷ repeating tile-and-joint module)
purchase tiles = ceil(geometric tiles × (1 + entered waste%))
boxes = ceil(purchase tiles ÷ tiles per box)
Coverage-per-box mode instead divides net area plus waste by the coverage printed on the carton. Purchased coverage and surplus use whole boxes. A diagonal-layout choice is recorded in the measurement plan but does not silently impose extra waste; enter an allowance for the actual pattern, room, cuts, breakage risk, and spare-tile plan.
Adhesive and grout are optional container estimates. Enter the selected manufacturer's coverage per container. The CUSTOM Building Products coverage chart shows why grout coverage changes with tile size and joint width.
For a 20 ft × 15 ft floor, 12 in square tiles, 1/8 in joints, and 10% entered waste, Planner reports the net area, geometric tiles, purchase tiles, whole boxes, purchased coverage, and surplus. Its diagram is an area map, not a cut-by-cut layout: it does not promise that every offcut can be reused or resolve centered grout lines, movement joints, trim, or substrate preparation.
Typical 12×12 in tile with ¼ in grout
| Room | Area | Tiles | +5% | +10% | Boxes of 12 |
|---|---|---|---|---|---|
| 10 ft × 10 ft | 100 sq ft | 96 | 101 | 106 | 8 |
| 20 ft × 15 ft | 300 sq ft | 288 | 303 | 317 | 24 |
| 6 m × 4 m, 30 cm tile, 5 mm gap | 24 m² | 258 | 271 | 284 | 26 of 10 |
Grout-joint width depends on the tile and installation plan. Enter the gap specified for your project; roofing tile and siding overlap instead, so those projects use a negative gap.
Room-order worksheet: 11 ft × 9 ft
Suppose a 99 sq ft room uses 12 × 12 in tiles, a 1/8 in grout gap, and boxes of 12 tiles at $36 per box. Enter the room dimensions, tile dimensions, gap, box size, and price per box in the Dimensions tab.
| Step | Calculation | Estimate |
|---|---|---|
| Floor area | 11 × 9 | 99 sq ft |
| Tile module | (12 + 1/8) × (12 + 1/8) | 147.016 sq in |
| Base tiles | ceil(99 × 144 ÷ 147.016) | 97 |
| With 5–10% extra | ceil(unrounded base × 1.05–1.10) | 102–107 tiles |
| At 10% extra | ceil(107 ÷ 12) | 9 boxes, or $324 |
This is an area estimate, not a cut-by-cut layout: it assumes offcuts can be used efficiently. Check the room's actual shape, border cuts, movement joints, and carton coverage before purchasing. The 10% in this example is an editable planning input rather than a universal recommendation. Complicated layouts may need a separate cut plan. If your tile carton is sold by square-foot coverage rather than tile count, use that printed coverage to verify the order.
Examples
Default 20 ft by 15 ft room
A 20 ft × 15 ft floor is 300 square feet. With 12×12 in tile and a ¼ in grout line, each tile covers 12.25×12.25 in (about 1.042 sq ft), so you need 288 pieces, or 24 boxes of 12. Plan on 303–317 tiles (26–27 boxes) so you have extras for cuts and a matching repair later.
30 cm tile on a 6 m by 4 m floor
A 6 m × 4 m room is 24 m². 30×30 cm tiles with a 5 mm grout line cover 0.305×0.305 m each, so you need 258 pieces. In boxes of 10 that is 26 boxes, or 28–29 boxes with 5–10% extra (271–284 tiles).
Formula
Lengths convert through metres (1 in = 0.0254 m, 1 ft = 0.3048 m). Each tile covers a module of tile + gap on both sides. Tiles are the area divided by that module, rounded up.
module = (tile_length + gap) × (tile_width + gap)
tiles = ceil(area / module)
boxes = ceil(tiles / tiles_per_box)
A positive gap is grout; a negative gap is overlap. Extra for waste is applied to the unrounded tile count, then rounded up:
tiles_5% = ceil(area / module × 1.05)
tiles_10% = ceil(area / module × 1.10)
Limits of an area estimate
The repeating tile-and-joint module estimates area coverage; it does not place individual rows, center grout lines, test border widths, or prove that an offcut can be reused. Nominal and actual tile dimensions may differ. Adhesive and grout coverage depend on the product, trowel, substrate, tile size, joint dimensions, and installation method, which is why those container estimates require manufacturer coverage entered by the user. The result excludes trim, movement joints, backer materials, waterproofing, labor, delivery, tax, and substrate repair.