How the flooring calculation works
- Floor area = room length × room width.
- Add waste: floor area × (1 + waste ÷ 100). Waste covers the offcuts at the ends of rows, cuts around door frames and pieces with defects.
- Boxes = area including waste ÷ coverage per box, rounded up to a whole box.
Flooring is only sold in whole boxes, so the coverage you buy is almost always a little more than the area including waste. The calculator shows how much will be left over.
Choosing a waste percentage
These are common rules of thumb. Your installer or the flooring manufacturer may recommend something different.
- 5–10%: straight-lay planks or tiles in a simple rectangular room.
- 10–15%: rooms with lots of corners, closets, doorways or pipes, or a diagonal layout.
- 15–20%: herringbone, chevron and other patterned layouts that need many angled cuts.
Many people keep a spare box after fitting, so a damaged board can later be replaced with one from the same production batch.
Rounding rules
- Boxes are always rounded up: 13.2 boxes means buying 14.
- Areas are shown to two decimal places (or fewer for large numbers). Every step uses the full, unrounded figures.
Measuring the room
Measure the longest and widest points of the room, wall to wall. Include the space under anything that is fixed after the floor goes down, such as some kitchen appliances, and exclude areas under fitted cabinets if the floor won't go under them. For rooms that aren't rectangular, split the floor into rectangles, calculate each, and add the results.