Flooring & Tile
Tile and Grout Calculator with Spacer Allowance
Enter the tiled area, tile size, physical spacer width, tile allowance, and the grout coverage printed for that exact tile and joint combination. The result keeps tile boxes and grout packages as separate rounded shopping-list lines.
Formula tested · Local units · No sign-up
Project inputs
Enter measurements
Use your preferred units. Results update automatically.
Show the calculation methodFormula, conversions, rounding, and assumptions+
Each tile occupies its own size plus one grout joint: a 12 × 12 in tile with a 1/8 in joint takes up 12.125 × 12.125 = 147.02 sq in, about 1.021 sq ft. The area is divided by that footprint to get the exact tile count.
A wastage allowance is then added for cuts, breakage and spares — 10% is typical for a straight lay, 15% for diagonal patterns — and the result is rounded up to a whole tile, then up again to whole boxes when you enter the tiles-per-box figure from the box label.
For grout, enter the square-foot coverage of one package from the product's coverage chart for the same tile size, joint width and joint depth. The calculator adds your explicit mixing/handling allowance and rounds up to a whole grout package.
Real-world example
Worked example: 10 ft × 8 ft floor, 12 × 12 in tiles, 1/8 in joints
- Area: 10 × 8 = 80 sq ft.
- Tile footprint: (12 + 0.125) × (12 + 0.125) = 147.02 sq in ≈ 1.021 sq ft.
- Exact count: 80 ÷ 1.021 = 78.36 tiles.
- Add 10% wastage: 78.36 × 1.10 = 86.19 → round up to 87 tiles.
- Boxes of 10: 87 ÷ 10 = 8.7 → round up to 9 boxes.
- If the selected grout package's matching coverage row says 100 sq ft, a 5% entered handling allowance makes 84 sq ft; 84 ÷ 100 = 0.84 → 1 grout package.
Buy 9 boxes (90 tiles) and 1 grout package for the illustrative 100 sq ft coverage input. Replace that grout coverage with the exact chart row for your product, tile and joint before buying.
Before you start
How to measure
- Measure the room's length and width in feet at the widest points; for L-shaped rooms, split into rectangles and add the areas in direct-area mode.
- Take the tile size and tiles-per-box count straight from the box label — nominal 12-inch tiles are sometimes slightly under 12 inches.
- Grout joints are commonly 1/8 in (0.125) for floor tile; rectified tile is often laid with tighter 1/16 in joints — enter what your installer plans to use.
- Read grout coverage from the selected manufacturer's chart for the exact tile size, thickness or joint depth, and joint width. A coverage row for a different tile can change the package count materially.
Local guidance
Notes for United States
- US tile is sized in inches — 12×12, 12×24, 18×18 floor tile and 3×6 subway wall tile are the common formats — and sold by the box with the coverage printed in square feet.
- Boxes state both tiles per box and sq ft per box; this calculator works from tiles per box, so use that figure from the label.
- Sales tax varies by state and locality and is entered manually; keep at least a few spare tiles from the same dye lot for future repairs.
Quick reference
Common US tile sizes (nominal)
| Format | Size | Typical use |
|---|---|---|
| Square floor | 12 × 12 in | Bathrooms, kitchens, entries |
| Plank / large format | 12 × 24 in | Open floors, showers |
| Large square | 18 × 18 in | Larger rooms |
| Subway | 3 × 6 in | Backsplashes, shower walls |
Nominal sizes for planning — actual dimensions and tiles per box are on the box label.
Good to know
Common mistakes to avoid
- Ignoring the grout joint — over a large floor the joints add up to noticeably fewer tiles than a joint-less division suggests.
- Ordering with no wastage allowance: every cut row, broken tile and future repair comes out of the same dye lot.
- Using 10% wastage for a diagonal or herringbone lay that realistically consumes 15% or more.
- Using a grout coverage figure for a different tile size, joint width, joint depth, or product package.
- Buying a later tile batch to top up — dye lots vary, so order everything at once.
Need help?
Frequently asked questions
How many 12×12 tiles do I need for 100 square feet?
With a 1/8 in grout joint each tile occupies about 1.021 sq ft, so 100 ÷ 1.021 = 97.9 tiles exactly. Adding 10% wastage gives 107.7, so buy 108 tiles.
How much extra tile should I buy for wastage?
10% is the usual planning allowance for a straight lay; use 15% for diagonal or herringbone patterns, small or irregular rooms, and large-format tile where each miscut costs more area.
How many bags or packages of grout do I need?
Find the coverage per package in the manufacturer's chart for your exact tile dimensions, joint width, joint depth and grout product, enter it here, and the calculator rounds the adjusted tiled area up to whole packages. Thinset, spacers and trim remain separate materials.
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About this calculator
- Written by:
- BuildMeasure Editorial Team
- Technically reviewed by:
- Pending independent technical reviewer (formula unit-tested; see methodology)
- Last reviewed:
- 2026-07-20
- Formula version:
- 1.2.0
- Region reviewed for:
- United States
- Spotted an error?
- Report a correction
Methodology
- The area to tile comes either from length × width or from a directly entered area. All arithmetic runs internally in SI units (metres and m²); regional units (inches, mm, ft²) are converted exactly on the way in and out.
- Each tile's effective footprint is (tile length + grout gap) × (tile width + grout gap) — the grout joint is counted once per tile, which is how a repeating grid actually consumes floor area.
- Tile count = area ÷ footprint, multiplied by (1 + wastage %), then rounded UP to a whole tile. When you enter tiles per box, boxes = tile count ÷ tiles per box, rounded UP to a whole box.
- Grout package count uses the manufacturer's coverage for the exact tile size, joint width, joint depth, grout product, and package size. The calculator adds only the grout handling allowance you enter, divides by that coverage, and rounds UP to a whole package; it does not invent a universal grout yield.
- The cost estimate uses the separately rounded tile and grout purchasing quantities and the prices you enter, then applies the tax rate only when both included products have prices. No prices are built in.
- The formula is covered by automated unit tests, including hand-calculated worked examples, and is versioned (see formula version on this page).
Sources & standards
- Unit definitions: 1 in = 25.4 mm and 1 ft² = 0.09290304 m² (exact definitions).
- Wastage allowances: 10% straight lay / 15% diagonal are standard planning allowances; confirm with your installer.
- Manufacturer grout coverage: MAPEI and Merkrete calculators show that grout coverage depends on tile size, joint width, joint depth and product; use the exact product chart rather than a universal default.
This tool provides a tile-and-grout material estimate for planning purposes only. It is not a quotation and does not calculate adhesive, trim, substrate preparation or waterproofing. Grout coverage varies with tile size, joint width, joint depth, product density and application; use the exact manufacturer coverage row and confirm quantities with your supplier.