How do I calculate how many tiles I need?

Multiply the room length by the room width to get the floor area in square feet. Then divide by the area of one tile (in square feet, including grout gap). Round up and add a 10% waste allowance for cuts and breakage.

What grout gap should I use for floor tiles?

Standard ceramic or porcelain floor tiles typically use a 1/8-inch (0.125 in) grout joint. Natural stone tiles often require wider joints of 3/16 to 1/4 inch to allow for irregularities.

How many tiles are in a box?

This varies by tile size. Smaller tiles (e.g., 4×4 in) may have 40+ tiles per box covering 5–7 sq ft, while larger tiles (e.g., 12×24 in) may have 5–10 tiles per box covering 15–20 sq ft. Always check the box label.

Why add a waste allowance for tiling?

Tiles break during cutting and installation. Diagonal or pattern layouts waste significantly more material during cuts. We recommend 10% for straight layouts and 15% for diagonal or herringbone patterns.

Should I include doors and windows in my tile area?

For floor calculations, windows do not affect the area. For wall tiles, subtract window and door openings but add back at least 5–10% because cuts near openings often produce unusable offcuts.

Flooring Planning Tools•Free Web App

Tile Calculator

Whether you are tiling a bathroom floor, kitchen backsplash, or outdoor terrace, our Tile Calculator gives you accurate tile counts and box requirements. Input your room dimensions, tile size, and grout joint width to avoid buying too many — or too few — tiles.

Getting your tile order right the first time saves money and prevents frustrating mid-project store runs. Our Tile Calculator factors in your room's exact dimensions, individual tile size, grout joint width, and a configurable waste percentage to give you an accurate tile count and box recommendation.

1 · Project Specifications

Room Dimensions

Room Length*12

Length of the floor or wall area to be tiled.

Length Unit

Room Width*10

Width of the floor or wall area to be tiled.

Width Unit

Tile Specifications

Tile Length*12

Length of a single tile (check packaging).

Tile Length Unit

Tile Width*12

Width of a single tile (check packaging).

Tile Width Unit

Grout Joint Width0.125 in

Width of grout lines between tiles (1/8 in is standard; 3/16 in for natural stone).

Options

Output Unit System

Imperial (sq ft / in)Metric (m² / cm)

Waste Allowance (%)10 %

Extra tiles to cover cuts, breakage, and pattern matching (10% is standard; 15% for diagonal layouts).

2 · Material Estimates

Estimation Results

Enter your measurements and click Calculate to see your estimate.

Estimates include recommended safety waste margins. Double-check measurements before purchasing materials.

Calculation Formulas & Methodology

Floor Area

Floor Area = Length × Width

Calculates the total surface area to tile in square feet.

Effective Tile Area

Effective Tile Area = (Tile Length + Grout) × (Tile Width + Grout)

Each tile occupies more space than its face area because it includes one grout joint on each side.

Tiles Required

Tiles = ⌈(Floor Area × (1 + Waste / 100)) / Effective Tile Area⌉

Divides the waste-adjusted area by the effective tile footprint, rounding up to the nearest whole tile.

How It Works

1Enter the room length and width (switch between feet, inches, meters, or cm).
2Enter your tile length and width (check the packaging label).
3Set the grout joint width (1/8 in is standard for most floor tiles).
4Adjust the waste allowance (10% for straight-set; 15% for diagonal layouts).
5Click Calculate to see your tile count and box requirements instantly.

Frequently Asked Questions

✓ Pro Tips

•Buy 10–15% more tiles than calculated. Tile dye lots change between production runs; ordering too few and coming back later may result in a noticeable color mismatch.
•For diagonal or herringbone patterns, increase your waste allowance to 15–20% to account for the larger corner cuts.
•Store extra tiles for future repairs. Even a few spare tiles can be invaluable when a single tile cracks years later.

⚠ Common Mistakes

•Not accounting for grout joints: Forgetting to add the grout gap to tile dimensions understates how many tiles you need, especially for small tiles with many joints.
•Ordering the exact count: Always order extra — tiles break, dye lots are discontinued, and repairs become impossible without spare tiles.
•Ignoring subfloor preparation: Tile installations over uneven or soft subfloors will crack. Ensure your subfloor deflects less than L/360 before tiling.

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