Tiles needed for an area (+ 10% waste).
Tiles needed = (area in sq ft ÷ tile size in sq ft) plus 10% waste for cuts and breakage.
For complex layouts or diagonal patterns, allow 15–20% waste.
The waste allowance exists because tiles at the edges of a room almost always need to be cut to fit, and cut pieces are rarely usable elsewhere — a larger tile size or an irregularly shaped room both tend to increase the waste percentage.
100 sq ft with 1 sq ft tiles = 100 + 10% = 111 tiles.
15–20% — more cuts mean more offcuts.
Yes — buy whole boxes and keep spares for future repairs.
Yes when possible — tile color and shade can vary subtly between manufacturing batches (called a 'lot' or 'dye lot'), which can be noticeable once installed if mixed.