Divide total floor/wall area by one tile area. Round up and add wastage (usually 5–10%) for cuts and breakage.
Tile area is measured edge-to-edge; grout lines slightly reduce usable tile area but are usually accounted for by standard wastage percentage.
Tile area = tile length × tile width (convert units to meters or feet consistently before calculation).
Yes — order extra tiles (5–10%) to cover cuts, breakage, and future repairs—especially for tiles that may be discontinued.