Flooring Calculator
Room square footage plus the waste allowance that decides whether you have enough, converted into the number of boxes to buy.
Flooring needed
198.0sq ft
- Floor area
- 180.0 sq ft
- With waste
- 198.0 sq ft
- Square metres
- 18.39
- Square yards
- 22.00
- Boxes
- 10
- Includes a 10% waste allowance. The bare figure is 180.00 sq ft.
- Ten per cent covers offcuts on a simple rectangular room. Allow fifteen for a diagonal or herringbone lay, or a room with several alcoves.
- Box coverage is printed on the carton and differs between ranges, so check yours rather than trusting the default.
About the flooring calculator
Floor area is the easy part. What actually decides whether you have enough flooring is the waste allowance, and it is the number most people guess at.
Every run of board ends in a cut, and the offcut is usually too short to start the next row. Ten per cent covers that in a plain rectangular room laid straight. A diagonal or herringbone pattern wastes considerably more because every board meets the wall at an angle, so allow fifteen. Rooms with alcoves, bays or several doorways sit at the higher end too.
Box coverage is an input because it differs between ranges, even from one manufacturer. A room needing 198 square feet takes ten boxes at twenty square feet each but only nine at 22, which is the difference between a spare box and none.
What it works out
- Square footage in feet, metres and yards
- Boxes to buy, at your carton's coverage
- A waste allowance for straight or diagonal lays
The formula
Boxes = (Length × Width × (1 + Waste)) ÷ Coverage per box
Floor area is the easy part: length times width. What decides whether you have enough is the waste allowance, and it is the number most people guess at.
Every run of flooring ends in a cut, and the offcut is usually too short to start the next row. Ten per cent covers that on a plain rectangular room laid straight. A diagonal or herringbone pattern wastes far more because every board meets the wall at an angle, so allow fifteen. Rooms with alcoves, bay windows or a lot of doorways sit at the higher end too.
Then divide by what one box covers. That figure is printed on the carton and differs between ranges even from the same manufacturer, so it is worth checking rather than assuming.
- Length and Width
- The room dimensions. Measure the widest points, including any alcoves you are flooring.
- Waste
- Extra to cover offcuts. Ten per cent straight, fifteen for diagonal or a complicated room.
- Coverage per box
- Square feet one carton lays, as printed on the box.
A worked example
A fifteen by twelve living room, straight lay, in boxes covering twenty square feet each.
That works out to 198.0 sq ft.
- Floor area
- 180.0 sq ft
- With waste
- 198.0 sq ft
- Square metres
- 18.39
- Square yards
- 22.00
- Boxes
- 10
Questions
How much extra flooring should I buy?
Ten per cent over the room area for a straight lay in a simple rectangular room, and fifteen for a diagonal or herringbone pattern, or a room with alcoves and several doorways. Running out mid-job risks a batch mismatch you cannot fix.
How do I measure a room that is not a rectangle?
Split it into rectangles, work out each one separately, and add them together. An L-shaped room is two rectangles; a room with a bay window is the main rectangle plus the bay.
Should I measure under the furniture?
Yes. Flooring goes down across the whole floor, so measure wall to wall and ignore what is standing on it.
What about doorways and closets?
Add them in if you are flooring through them. A doorway threshold takes roughly a square foot; a closet is its own small rectangle.
Why does box coverage matter so much?
Because you buy whole boxes. A room needing 198 square feet takes ten boxes at twenty square feet each, and the same room takes nine at 22 square feet. Checking the carton is the difference between one spare box and none.
Should I buy an extra box beyond the waste allowance?
It is worth it for anything you cannot easily rebuy. Colours and finishes shift between production runs, so a spare box from the same batch is the only reliable way to repair a damaged board in five years.