How to Calculate Tiles for a Floor (Step by Step)

Quick answer:Multiply the floor’s length × width to get square footage, divide by the square footage of one tile, add 10% waste (15% for diagonal or large-format), and round up to full boxes. A 180 sq ft floor with 24×24 in tiles (4 sq ft each) needs 45 tiles + 10% = 50 tiles, or 13 boxes of four.

Getting the floor count right before you buy saves money and a second trip to the store. Here’s how to measure, choose a tile size, and handle the parts people usually miss — or use the tile calculator for an instant result.

What to measure

For a rectangular room you need just two numbers: length and width, measured wall to wall at the longest points. For L-shaped or irregular rooms, split the floor into rectangles, measure each, and add the square footages. This is the same approach covered in how many tiles do I need.

Choosing a floor tile size

Larger tiles mean fewer pieces and fewer grout lines, but they need a flatter subfloor and produce bigger offcuts at the walls. Common floor sizes and their coverage:

• 12 × 12 in — 1.00 sq ft (easiest to calculate)
• 12 × 24 in — 2.00 sq ft (popular modern look)
• 18 × 18 in — 2.25 sq ft (good for larger rooms)
• 24 × 24 in — 4.00 sq ft (large-format, fewer pieces)

Worked example: 15 × 12 ft living room, 24×24 tile

Diagonal layouts need more tile

Setting tile at 45° creates triangular cuts at every wall, so use a 15% waste factor instead of 10%. On the same 180 sq ft floor:

See how much extra tile to buy for the right waste factor by layout and tile type.

Subtracting islands and built-ins

Fixed islands, pillars, and large built-ins can be deducted from the floor area. Measure each footprint (length × width) and subtract it from the total. The tile calculator has an opening-deduction feature for exactly this.

Tips for an accurate floor count

• Measure twice before ordering.
• Add at least 10% waste — more for diagonal or large-format tile.
• Buy all tile from the same dye lot to avoid color variation.
• Keep leftovers; matching tile for a repair years later is difficult.
• Check the coverage printed on the box — it varies by product.

Frequently asked questions

How do I measure a floor for tile?

Measure the room's length and width at the longest points, wall to wall, in feet, and multiply them for square footage. For L-shaped or irregular floors, divide the space into rectangles, measure each, and add the areas together.

How many boxes of floor tile do I need?

Work out your total tiles including waste, then divide by the number of tiles in a box and round up to the next full box. Buying full boxes avoids running short mid-install on a dye lot that may no longer be in stock.

How much waste should I add for a floor?

Use about 10% for a straight or grid layout. Add 15% for diagonal layouts and large-format tile (18 in and larger), which produce more and larger offcuts at the walls.

Do I subtract islands and cabinets from the floor area?

Yes, subtract the footprint of anything fixed that you won't tile under, such as a kitchen island or built-in cabinetry. Measure each footprint (length × width) and deduct it from the total floor area.

Enter your floor dimensions into the tile calculator to get tile count, waste, boxes, and an optional cost estimate. Tiling a backsplash too? See how to calculate backsplash tile.