How to measure a room’s area
- Measure the length and width of the floor at its widest points, wall to wall. Measure at floor level, under the skirting if you can.
- If the room isn’t a rectangle, sketch it and split it into rectangles, triangles and curves with straight lines.
- Add each piece above. Add things you won’t cover, such as a fitted unit or a chimney breast, and tick Subtract.
- Add a waste margin for cutting, and a price per area if you have a quote.
The formulas
- Rectangle = length × width.
- Triangle = base × height ÷ 2, where the height is measured at right angles to the base.
- Circle = π × radius², where the radius is half the diameter.
- Half circle (such as a curved bay) = π × radius² ÷ 2.
- Quarter circle = π × radius² ÷ 4.
One square metre is 10.7639 square feet. One square yard is 9 square feet, or about 0.836 m².
Worked example
An L-shaped living room: a main area 5 × 4 m and an alcove 2 × 1.5 m, with a chimney breast 1.2 m wide and 0.4 m deep.
- Main: 5 × 4 = 20 m². Alcove: 2 × 1.5 = 3 m². Together 23 m².
- Chimney breast: 1.2 × 0.4 = 0.48 m², so the floor is 23 − 0.48 = 22.52 m² (about 242 sq ft).
- With 10% extra: 22.52 × 1.1 = 24.77 m² to buy.
Choose Try an example above (with metric selected) to load these numbers.
Assumptions and limitations
- Walls are assumed to meet at right angles within each rectangle. For a very out-of-square room, measure both ends and use the larger figure.
- The waste margin is a simple percentage. Products sold in boxes or rolls need whole units; use the flooring, tile or wallpaper calculators for those.
- The sketch is scaled to fit the screen and page, not printed at a physical scale.
Frequently asked questions
How do I work out the square footage of a room?
Multiply the length by the width. A room 12 ft long and 10 ft wide is 12 × 10 = 120 square feet. In metric, a room 4 m × 3 m is 12 m². If the room isn’t a rectangle, split it into rectangles and other simple shapes, work out each one and add them together.
How do I measure an L-shaped room?
Split it into two rectangles with one straight line. Measure each rectangle’s length and width, and add the two areas. It doesn’t matter which way you split it, as long as the two pieces don’t overlap.
How do I convert square metres to square feet?
One square metre is about 10.764 square feet, and one square foot is about 0.0929 m². The calculator shows both, plus square yards (9 sq ft), which some carpet sellers use.
How much extra should I add for waste?
Should I subtract fitted cupboards and kitchen units?
For flooring, it depends whether the floor goes under them. Many people floor under freestanding furniture but not under fitted units or a kitchen island that’s already in place. Add those as pieces and tick “Subtract”.
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