What it works out
Count the cartons of flooring a room needs. Enter the room size and what one carton covers, as printed on the box. Waste is added first, then the total is rounded up once to whole cartons, and you see what is left over. Waste starts at the usual figure for the trade and goes up for diagonal layouts; change it in the tool. Buy from one batch so the colour matches.
The formula
- Cartons
- area × (1 + waste) ÷ carton coverage, rounded up
In words: Cartons = area times one plus waste, divided by carton coverage, rounded up
Worked example
A 15 ft by 12 ft room with cartons covering 20 ft² each and 10% waste
- Length 15 ft
- Width 12 ft
- Carton covers 20 ft²
- Waste 10%
- Area = 15 × 12 = 180 ft²
- With waste = 180 × 1.10 = 198 ft²
- Cartons = 198 ÷ 20 = 9.9, rounded up to 10
10 cartons cover 200 ft², leaving 2 ft² spare beyond the waste allowance.
Good to know
- Buy from one batch so the colour matches.
- Waste goes up for diagonal layouts.
- A calculator, not a building-code check: confirm local rules with your building authority.
Questions
Why round up to whole cartons?
Cartons are not sold in part.
What about carpet or vinyl rolls?
The tool also works out roll lengths.