Square metre calculator

How to use

The area of a rectangle is width times length, and in construction that number decides how much flooring, paint or tile to buy. The waste percentage exists because cuts, breaks and leftovers are part of real work: buying exactly the measured area almost always leaves the job short.

• Buy flooring, tiles or paint with a realistic quantity.
• Quote a room or a wall before a renovation.
• Check the area announced for a property against its measurements.

1. Measure the width and the length in metres.
2. Enter the waste percentage you expect for the material and the cut pattern.
3. The result gives the net area and the area with the waste added.

Formula

Area (m²) = width × length · With waste = area × (1 + waste ÷ 100)

Example

A room of 3 m by 4 m has 12 m². With 10% waste the purchase becomes 13.2 m².

Limitations

• The shape is treated as a rectangle; L-shaped rooms should be split into rectangles and added up.
• Doors, windows and other openings are not subtracted — measure them and discount them by hand when it matters.

Frequently asked questions