Exact count is not the buy count
The calculator gives two numbers: the mathematical tile count for the area, and the realistic buy count with a waste allowance. Tiles crack in the box, cuts go wrong, and future repairs need spares — 10% waste is the standard for a straight lay, 15% for diagonal, herringbone or rooms with many jogs.
Dye lots are forever
Tile from different production runs varies slightly in color and texture. Buying the full quantity — plus the waste — from one dye lot matters more than any other tile-buying rule, because you cannot top up from a different lot without seeing the seam. This is why you buy all at once, not in stages.
Measure the awkward bits
Break L-shaped rooms into rectangles and add them. For walls (kitchen backsplash, shower surround), the same math applies: width × height of each section, minus window and niche openings, then the waste factor.
Sources and standards
Where these figures come from
Every formula on this page is implemented from the published reference material below. Where a value depends on a regional code, the calculator lets you override it rather than assuming one jurisdiction.
- Tile Council of North America — the TCNA Handbook installation methods referenced here.
- Carpet & Rug Institute — carpet installation standards and performance testing.
- US Environmental Protection Agency — volatile organic compound limits for paints and coatings.
Figures, formulas and reference tables last verified: 19 September 2026.