A worked example
A 200 sq ft room tiled with standard 12×12 inch tiles, plus a 10% waste factor, needs 221 tiles.
Frequently asked questions
Why include a waste factor at all?
Cutting tiles to fit room edges, corners, and obstacles always produces some unusable offcuts — a waste factor builds that loss into the order so you don't run short partway through installation.
Should I round up or down on the final tile count?
Always round up — buying one extra tile is a minor cost, while running short mid-project (especially with a dye-lot match issue on a reorder) can be a much bigger headache.