How much tile do I need?
To work out how much tile to buy, you need four numbers: the area you're covering, the size of one tile plus its grout joint, a waste allowance for cuts and breakage, and the square feet in one box.
Step 1: Measure the area. Multiply length by width for each rectangle, in feet. For an L-shaped room, split it into two rectangles and add them. For a 10 ft × 12 ft bathroom floor that's 120 sq ft. Subtract anything that won't be tiled, like a vanity footprint or a tub. The result is your net area.
Step 2: Find the tile's footprint. A tile covers its own face plus half the grout joint on each side. Add the joint width to each tile dimension, multiply, and divide by 144 to get square feet. A 12 × 24 in tile with a 1/8 in joint covers (12.125 × 24.125) ÷ 144 ≈ 2.03 sq ft.
Step 3: Add waste. Cuts at walls, around fixtures and at pattern edges use up extra tile. Our presets match the flooring waste factor calculator: about 10% for a simple straight layout, 12% for multiple rooms and jogs, 15% for diagonal or large-format tile, and 20% for herringbone or chevron. These are planning starting points, not guarantees. Very small rooms, many corners and natural stone with variation can all need more. Many people also keep a few spare tiles for future repairs, because a later production run may not match.
Step 4: Round up to whole boxes. Tile is sold by the box, and each box label lists its coverage in square feet. Divide area-with-waste by box coverage and always round up.
Worked example: 120 sq ft × 1.10 = 132 sq ft to buy. 132 ÷ 2.03 ≈ 65 tiles (60 without waste). If a box covers 16 sq ft, 132 ÷ 16 = 8.25, so you order 9 boxes (144 sq ft). Subtract a 3 × 2 ft vanity and the net area is 114 sq ft: 125.4 sq ft with waste, 62 tiles and 8 boxes.
Tile square footage calculator for multiple rooms
Add each room or wall as a separate area and the calculator adds them up. For a shower, add each wall (width × height) and the floor. Subtract the niche opening only if you're finishing it with a different material. Browse bathroom tile, porcelain and natural stone.
Floor tile vs. backsplash tile
The math is the same. Backsplashes are small, which makes waste matter more: outlets, window returns and end cuts use more tile per square foot, so many people plan toward the higher end of the waste range. Mosaic sheets are usually sold by the sheet, so enter the sheet size as the tile size. See our kitchen backsplash tile and shower tile collections.
Before you order
Estimates are only as good as your measurements. Ask your installer to confirm quantities, especially for patterns, large-format tile or stone. Northern Lights Design supplies materials only. We don't install, so you hire the installer of your choice, and we help you choose the product, quantities, trim and setting materials. Planning plank flooring instead? Use the same square footage with the flooring waste factor calculator, and compare luxury vinyl, hardwood or tile vs. luxury vinyl. For grout and levelers, see installer & pro supplies.