Worked example: an 8 × 5 ft bathroom floor
Hypothetical educational example of a rectangular bathroom floor. It is not a waterproofing specification and not a client bathroom. Ten tiles per box is the calculator default used as a scenario, not a carton we verified for a named product.
Inputs
| Length | 8 ft |
|---|---|
| Width | 5 ft |
| Tile | 12 × 12 in |
| Joint | 1/8 in |
| Pattern | straight, so the blank waste field uses 10% |
| Tiles per box | 10 (scenario assumption) |
Arithmetic
- Area = 40 sq ft.
- Face plus joint = 12.125 × 12.125 in. Tiles = 40 × 144 ÷ 147.015625 = 39.179.
- The calculator rounds the uncut count up to 40 before it labels a waste allowance, then rounds 39.179 × 1.10 = 43.097 up to 44 tiles needed.
- Boxes = 44 ÷ 10 = 4.4, which rounds up to 5 boxes = 50 tiles.
Required, waste and purchase
- Required
- 44 tiles, which already includes the 10% layout allowance (displayed as 4 tiles over the rounded 40).
- Purchased
- 5 boxes = 50 tiles if, and only if, the carton holds 10. The 6 tiles between 50 and 44 are spare from full boxes, not a second waste percent.
- Units
- US feet and inches. The thinset line on the tile result is a rough guide only.
Assumptions
- No tub or cabinet deduction.
- Straight-lay waste stays at the pattern default of 10% because the waste field is blank.
What this example does not decide
- Does not specify a waterproofing membrane, a notch trowel, or grout pounds. Open the thinset and grout calculators for those.
- Not a named tile SKU.
Where to go next
- Tile calculator — Run these inputs
- Thinset calculator — Trowel coverage, not the rough line on the tile page
- Grout calculator — Joint width and tile size
- Tile quantities topic — Layout waste method
- Tile waste guide — Why the percent changes with pattern
Questions
Why is the waste allowance 4 tiles and not 4.4?
The calculator first rounds 39.179 up to 40, then rounds the 10% quantity up to 44. The allowance it prints is 44 − 40 = 4. The order is still 44 tiles before the box rounding.
Is 10 tiles per box a manufacturer fact?
No. It is the imperial default on the calculator, used here so the box math is visible. Replace it with the number on the carton you buy. The 44-tile requirement does not change when the carton size changes; the box count does.
Sources
- Tile calculator pattern defaults on this site — accessed 2026-11-09: “Defaults: straight 10%, offset 12%, diagonal 15%, herringbone 20%.”