How the calculator works
Tiles = (area × (1 + waste)) ÷ area per tile, rounded up. Waste isn't padding. It's the cut pieces at every wall, the tiles that crack in the wet saw, and the spares you'll want in the attic. Thinset is figured at one 50 lb bag per 65 sq ft, a realistic average for ¼″–½″ notched trowels.
Worked example: a 120 sq ft bathroom floor in 12×24 tile with 10% waste needs 132 sq ft of coverage = 66 tiles. If boxes hold 15.5 sq ft, that's 9 boxes; plus 3 bags of thinset.
Setting the right waste factor
- 10%: straight (grid) lay in a simple rectangular room.
- 15%: diagonal, herringbone, or 50% offset patterns; every border tile is a diagonal cut.
- 20%: small rooms, rooms with many jogs/niches, or large-format tile where one bad cut costs 4 sq ft.
Beyond the tile
- Large-format tile (any side ≥ 15″) wants a ½″ trowel, back-buttering, and a very flat floor, so budget self-leveler if the slab dips more than ⅛″ in 10 ft.
- Offset rule: long planks should be offset a third, not half. 50% offsets on 24″+ tile telegraph lippage at every joint.
- Grout: a 10 lb bag typically does 60–100 sq ft of floor tile with standard ⅛″–3/16″ joints; wide-joint or small tile burns much more.