Key takeaways
- Tile count = the area to cover ÷ the area of one tile, plus a waste allowance.
- Add 10% waste for straight layouts and 15% for diagonal or patterned ones.
- A 50 lb bag of thinset covers about 95 sq ft with a 1/4″ square-notch trowel.
- Larger tiles need a bigger notch and back-buttering, so coverage per bag drops sharply.
How to estimate tile
Tile count = the area to cover ÷ the area of one tile, plus a waste allowance. First convert one tile's dimensions to square feet, then divide the area you're covering by that figure and round up. The waste allowance covers the cuts, breakage, and trimmed edges that every real job produces — never order the bare count.
Tile size is entered in inches because that's how tile is sold, so width × length is divided by 144 to convert square inches to square feet before dividing into the area.
Worked example: a 10 × 8 floor with 12 × 12 tile
For a 10 ft × 8 ft floor, the area is 10 × 8 = 80 sq ft. A 12 × 12 tile is (12 × 12) ÷ 144 = 1 sq ft each. At 10% waste, that's 80 × 1.10 = 88 sq ft to cover, so 88 ÷ 1 = 88 tiles. Thinset works out to 80 ÷ 95 = 1 bag (rounded up). Bump the waste to 15% for a diagonal layout and the count rises to 92 tiles.
Thinset coverage by trowel size (per 50 lb bag, approx.)
| Trowel notch | Typical tile | Coverage per 50 lb bag |
|---|---|---|
| 1/4 × 1/4 in square-notch | Small tile, mosaics | ≈ 95 sq ft |
| 1/4 × 3/8 in | Medium tile | ≈ 75 sq ft |
| 1/2 × 1/2 in | Large tile | ≈ 45 sq ft |
| 3/4 in U-notch | Large-format tile | ≈ 40 sq ft |
Picking the right trowel
The notch size sets how much thinset goes down, so it directly drives coverage. Larger tiles need a larger notch trowel — and usually back-buttering — for full coverage, which is why a bag that covers 95 sq ft under small tile may cover only 40 sq ft under large-format. Match the trowel to the tile, and buy thinset to the coverage in the table above rather than to a single rule of thumb. For sheet flooring or planks instead of tile, use the flooring calculator.
Frequently asked questions
How many tiles do I need?
Area ÷ the size of one tile, +10% waste, rounded up. A 10×8 floor (80 sq ft) in 12×12 tile needs about 88 tiles.
How much thinset for tile?
A 50 lb bag covers ~95 sq ft with a 1/4″ square-notch trowel; larger tiles and bigger notches use more.
How much waste should I add?
About 10% for a straight grid layout and 15% for diagonal or patterned layouts, which make more cuts. Round up to full boxes.
How many 12×12 tiles for a 10×8 floor?
80 sq ft at 10% waste = 88 tiles, and one 50 lb bag of thinset (80 ÷ 95, rounded up).
What size notched trowel should I use?
1/4 × 1/4 in for small tile, 1/4 × 3/8 in for medium, and 1/2 × 1/2 in or 3/4 in U-notch for large-format tile.
Do large-format tiles need more thinset?
Yes — they need a bigger notch and back-buttering, so a bag covers about 40–45 sq ft instead of ~95.
Thinset coverage figures follow manufacturer trowel charts — Custom Building Products publishes coverage by trowel size. Actual coverage varies with substrate flatness and back-buttering.
Last reviewed June 2026