How to work out square metres
Square metres (m²) measure area: how much floor, wall or ground something covers. For a rectangular room you multiply the length by the width, both in metres. A room 4m long and 3.5m wide is 4 × 3.5 = 14m². The calculator does the same sum for each shape and adds them together:
rectangle or square = length × width
L-shape = (overall length × overall width) − (cut-out length × cut-out width)
circle = 3.1416 × (diameter ÷ 2)²
triangle = base × height ÷ 2
square feet = m² ÷ 0.0929 (or m² × 10.764)
If you measured in feet, choose "Feet" and the calculator converts the result to m² for you. One square foot is exactly 0.09290304m², so one square metre is about 10.764 square feet.
How to measure an L-shaped room
Measure the full length and full width of the room as if it were a rectangle, then measure the "missing" corner that isn't part of the room. Take the missing piece away from the full rectangle. For a lounge 6m × 5m with a 2m × 2m corner taken out by a hallway:
- Full rectangle: 6 × 5 = 30m²
- Missing corner: 2 × 2 = 4m²
- Room area: 30 − 4 = 26m², or 279.9ft²
You can also split an L-shape into two rectangles and enter them as two areas. You get the same answer either way.
Worked example: two rooms and a round rug area
Say you're pricing new flooring for the 26m² L-shaped lounge above plus a circular bay 3m across, at £25 per m²:
- Lounge: 26m²
- Circle: 3.1416 × 1.5² = 7.07m²
- Total: 33.07m² (355.9ft²)
- Cost at £25 per m²: £826.71
Flooring and tiles also need extra for cuts, so add 5 to 10% in the "Extra for waste" box. With 10% extra the same job is 36.38m², or £909.39.
Square metres to square feet
| Square metres | Square feet | Example |
|---|---|---|
| 1m² | 10.8ft² | 1m × 1m |
| 7.5m² | 80.7ft² | Box room, 3m × 2.5m |
| 14m² | 150.7ft² | Double bedroom, 4m × 3.5m |
| 20m² | 215.3ft² | Living room, 5m × 4m |
| 50m² | 538.2ft² | Garden, 10m × 5m |
| 100m² | 1,076.4ft² | Plot, 10m × 10m |
Tips for measuring a room
- Measure at floor level from wall to wall, and into door recesses if the flooring goes under the door.
- Measure twice in different places. Older houses are rarely square, so use the longer measurement.
- Bay windows: measure the main room as a rectangle, then add the bay as a separate rectangle, triangle or half a circle (enter the full circle and halve it).
- Convert centimetres to metres by dividing by 100, so 350cm is 3.5m. Convert inches to feet by dividing by 12.
- House sizes: an Energy Performance Certificate (EPC) gives the total floor area in m². Divide by 0.0929 if you want it in square feet.
Once you know the area, the flooring calculator turns it into packs of laminate or vinyl, the tile calculator works out tiles and boxes, and the paint calculator does the walls.
Frequently asked questions
How do I work out square metres of a room?
Measure the length and width in metres and multiply them. A room 4m × 3.5m is 14m². For an L-shaped room, work out the full rectangle and take away the missing corner.
How many square feet are in a square metre?
One square metre is 10.764 square feet. To convert m² to ft², multiply by 10.764; to go from ft² to m², multiply by 0.0929.
How do I work out square metres from centimetres?
Convert each measurement to metres first by dividing by 100, then multiply. A 250cm × 180cm area is 2.5 × 1.8 = 4.5m². Multiplying the centimetres gives square centimetres, and there are 10,000cm² in 1m².
How do I calculate the area of a circle in square metres?
Halve the diameter to get the radius, square it and multiply by 3.1416. A circular patio 3m across is 3.1416 × 1.5 × 1.5 = 7.07m².
How much extra flooring should I buy?
Add about 5% for a simple rectangular room and 10% or more for L-shaped rooms, lots of doorways or a diagonal or herringbone layout.
Last reviewed October 2026 using 2026/27 figures. This calculator gives an estimate for guidance only.