How to use this calculator
- Measure the room. Length × width in feet. For irregular rooms, break into rectangles and add the results.
- Pick tile size. 12×12, 18×18, 24×24, or any custom size. Larger tiles waste less in cuts but need a flatter subfloor.
- Add 10% waste (15% for diagonal). Straight lay = 10%. Diagonal or herringbone = 15–20% because of the angled cuts at every wall.
- Get the box count. Boxes are typically 10–20 ft² each. Always buy a couple of extra boxes for future repairs from the same dye lot.
Formula
Square feet = (Length × Width) + 10–15% waste
Worked example
A 10×12 ft bathroom is 120 ft². Add 10% waste = 132 ft². For 12×12 tiles in 16 ft² boxes, that is 9 boxes. Plus 50 lbs of thinset and 10 lbs of unsanded grout for the joint width.
Tips for accurate results
- Lay 24-hour dry first to check the layout against the room before mortaring anything down.
- Center the layout so cut tiles end at the walls, not at the doorway.
- For wet rooms (showers, bathrooms with floor drains), use porcelain — it absorbs less water than ceramic.
- Match thinset to tile: large-format and porcelain need a polymer-modified thinset.