Square metre calculator for quotes and orders
Work out the area of a room, a lawn, a roof slope or a patio in square metres, square feet and square yards, from whatever units your tape measure shows. Free, no account, and your sizes stay in this browser, so they are there when you come back. Nothing is sent to us.
- Rectangles, triangles and circles, added up
- Measure in m, cm, mm, feet or inches
- Converts ft², yd² and m² either way
Pick the unit you measured in and enter each part of the space, or convert an area you already have, such as square feet to m².
2 areas, added up
Convert an area you already have
18.58 m² = 200 ft² = 22.22 yd²
The working
| Area 1 | 15.12 m² |
|---|---|
| Area 2 | 4.32 m² |
| Total | 19.44 m² |
Measure each wall or floor at its longest and widest. For materials, take the area to the paint, flooring, tile or turf calculators.
How to work out square metres: the sum
Multiply the length by the width, both in metres, and the answer is the area in square metres (m²). A room 4.2m long and 3.6m wide is 15.12m². If the space is not a simple rectangle, split it into rectangles, triangles and circles, work out each one, and add them together. The tool does the same, and its working lists each area and the total.
It opens on an L-shaped kitchen-diner, measured as two rectangles: the main room at 4.2m by 3.6m, and the dining end at 2.4m by 1.8m.
- Main room: 4.2 × 3.6 = 15.12m².
- Dining end: 2.4 × 1.8 = 4.32m².
- Total: 15.12 + 4.32 = 19.44m².
- In square feet: 19.44 ÷ 0.09290304 = 209.25ft².
- In square yards: 19.44 ÷ 0.83612736 = 23.25yd².
Triangles, circles and awkward rooms
Almost any floor, wall or garden can be measured as a handful of three shapes. Draw a rough sketch first, mark where you will split it, and measure each piece on its own. A five-minute sketch saves a second visit to re-measure.
Triangle
Base times height, halved. The height is measured square to the base, not along the sloping edge. A gable end 7.2m wide and 2.4m from eaves line to ridge is 7.2 × 2.4 ÷ 2 = 8.64m².
Circle
π times the radius squared, where the radius is half the diameter. Measure straight across through the centre. A round patio 3m across is 3.1416 × 1.5 × 1.5 = 7.07m², or 76.09ft².
L shapes and alcoves
Split into rectangles that do not overlap, then add them. Measure each alcove and bay as its own piece. Where a chimney breast sticks into the room, measure the floor around it as separate rectangles rather than taking it off afterwards.
Odd angles
A room with one wall off square can be split into a rectangle and a triangle. Measure the long side and the short side at both ends: the difference is the base of the triangle.
Square feet, square yards and metric
One square metre is 10.764 square feet, and one square foot is 0.0929m². Those figures are exact because the foot is defined as exactly 0.3048m: the Weights and Measures Act 1985 sets the yard at 0.9144m, with the foot a third of it and the inch a thirty-sixth, and NIST's conversion tables list the foot at 0.3048m, the inch at 0.0254m and the square foot at 0.09290304m², all marked exact.
Older customers and older plans often give sizes in feet and inches. Convert the inches into a decimal of a foot before you enter them: 6 inches is 0.5ft, 3 inches is 0.25ft, 9 inches is 0.75ft. Or set Measured in to Inches and enter everything in inches. A bedroom of 12ft 6in by 10ft is 12.5 × 10 = 125ft², which is 11.61m². Entered as 150in by 120in, it gives the same 11.61m².
Centimetres and millimetres catch people out because the area shrinks by the square. 450cm by 320cm is 4.5m by 3.2m, so 14.4m², not 144,000. The calculator converts each measurement to metres first, then multiplies, so you can enter the numbers straight off the tape.
- 1m² = 10.7639ft² (1 ÷ 0.09290304).
- 1ft² = 0.0929m² (0.3048 × 0.3048).
- 1m² = 1.1960yd², and 1yd² = 0.8361m² (0.9144 × 0.9144).
- 100ft² = 9.29m², 750ft² = 69.68m², 1,000ft² = 92.90m².
Measuring for a quote or an order
The area is the starting point, not the order. Every material calculator works from it, then adds the cuts and waste for that material. Get the square metres right once, write them on the job sheet, and use the same figure for the quote, the order and the invoice.
Measure to the nearest centimetre and round up, not down. Take the widest point of each wall, as rooms are rarely square. Measure into door reveals and bay windows if the floor runs into them. On a quote, say what the area figure covers, so nobody argues later about whether the hallway was included.
Floors
The same room sizes go into the flooring calculator for laminate, engineered wood or LVT packs, the carpet calculator for roll lengths, or the tile calculator for tiles, adhesive and grout. Each adds its own waste for cuts.
Walls and ceilings
Wall area is length times height, less doors and windows. The paint calculator does that subtraction and the coats for you, and the plasterboard calculator turns the area into boards and screws.
Outside
A lawn goes into the turf calculator, a patio into the paving calculator. For a depth of gravel, soil or concrete, you need cubic metres: the cubic metre calculator takes the length, the width and a depth in millimetres.
Where this tool stops short
It works out flat areas from the sizes you give it, and it is only as good as your tape. It does not add waste for cuts unless you put a percentage in the optional Add for waste box, which starts at 0%. Use the material calculators for that, as the right allowance depends on the material and the pattern.
- Slopes: the area of a sloping roof or bank is bigger than its plan area. Measure along the slope, not across the drawing.
- Walls with openings: take doors and windows off yourself, or use the paint calculator, which does it.
- Curves other than circles: split a curved bed into rectangles and triangles, or treat it as part of a circle, and accept the answer is an estimate.
- Not a survey: it is a measuring aid for quotes and orders. For the floor area of a property for sale, a lease or planning, use the measured survey or the drawings.
Common questions
How do I calculate square metres?
Measure the length and the width in metres and multiply them. A floor 5m by 3.5m is 17.5m². For an awkward shape, split it into rectangles, triangles and circles, work out each, and add them up.
How big is a 10 square metre room?
About the size of a small double bedroom. It could be 4m by 2.5m, 5m by 2m, or a square about 3.16m each way. In imperial, 10m² is 107.6 square feet.
How much is 1 square foot in square metres?
0.09290304m², exactly, because a foot is exactly 0.3048m. Multiply square feet by 0.0929 to get square metres, or divide square metres by 0.0929 to get square feet.
Is 1 square metre 100 square feet?
No. One square metre is about 10.76 square feet. 100 square feet is 9.29m². The mix-up usually comes from 1m being 100cm: a square metre is 100cm by 100cm, which is 10,000cm².
How do I convert cm to m²?
Divide each measurement by 100 to turn it into metres, then multiply. 280cm by 360cm is 2.8m by 3.6m, which is 10.08m². Multiplying the centimetres first gives square centimetres: divide that by 10,000.
What is the area of a circle in m²?
Halve the diameter to get the radius, square it, and multiply by π (3.1416). A circle 2m across has a radius of 1m, so its area is 3.14m². A circle 4m across is 12.57m², four times as big, not twice.
How do I measure an L-shaped room?
Split it into two rectangles that do not overlap. Measure each, multiply its length by its width, and add the two answers. In the calculator, press Add another area for the second one and it adds the two for you.
How much extra should I order on top of the area?
It depends on the material and the layout, so the waste box here starts at 0% and each material calculator applies its own figure. A straight-laid floor needs less than a diagonal or herringbone one, where every edge piece is a cut.
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