Square Meter Calculator guide
Square Meter Calculator: How to Work Out Square Metres
Use our square meter calculator to work out an area in m² from metres, centimetres or feet, convert to square feet, and price flooring, turf or paving.
By the AllCalculator editorial teamUpdated 15 October 20263 min read
Square metres come up whenever you're buying something to cover a surface: flooring, carpet, turf, paving, paint or wallpaper. Get the area right and you'll buy the right amount first time. Get it wrong and you're either short or paying for extra you don't need.
Our Square Meter Calculator works out the area in square metres (m²) for rectangles, triangles and circles, converts it to square feet and prices the job for you.
How to work out square metres
Rectangles and squares
Area = length × width
A room 5m long and 4m wide is 5 × 4 = 20m².
Triangles
Area = base × height ÷ 2
The height is measured at right angles to the base. A triangle with a 4m base and 3m height is 4 × 3 ÷ 2 = 6m².
Circles
Area = π × radius²
The radius is half the diameter. A 3m circular patio has a radius of 1.5m, so its area is 3.142 × 1.5 × 1.5 = about 7.07m².
L-shaped and irregular rooms
Split the space into rectangles, work out each one, then add them together. For a room with a bay window, measure the main room and the bay separately.
Measuring in centimetres or feet
Convert your measurements to metres first, or let the calculator do it:
- Centimetres to metres: divide by 100. 450cm is 4.5m.
- Millimetres to metres: divide by 1,000.
- Feet to metres: multiply by 0.3048.
- Square metres to square feet: multiply by 10.764. 20m² is about 215 sq ft.
Don't convert an area with a length conversion. Because area is two dimensions, 1m² is 10.764 sq ft, not 3.28.
How to use the calculator (Square Meter Calculator)
- Choose the shape: rectangle, triangle or circle.
- Choose the unit you measured in.
- Enter the measurements.
- If you have several identical areas, enter how many.
- Optionally, enter a price per m² to see the total cost.
You'll see the area in square metres, square feet, square yards and hectares, the area with 10% extra for waste, and the cost if you entered a price.
A worked example
With the calculator's default settings, a room is 5m × 4m:
- Area: 5 × 4 = 20m²
- In square feet: 20 × 10.764 = 215.28 sq ft
- With 10% extra for cutting and waste: 22m²
If laminate flooring costs £20 per m², the room costs £400, or £440 with the extra.
How much extra to buy
Most materials need extra to allow for cutting, mistakes and pattern matching:
- Laminate and wood flooring: around 10%.
- Tiles: 10% to 15%, more for diagonal layouts.
- Carpet: depends on roll width, so ask the supplier to measure.
- Turf: around 5% to 10%.
For other jobs around the home, our Concrete Calculator works out volume for a base, our Plasterboard Calculator counts sheets, and our Driveway Cost Calculator and Resin Patio Cost Calculator price larger areas.
Frequently asked questions
How do I calculate square metres?
Multiply the length by the width, both in metres. A space 3m by 2.5m is 7.5m².
How many square feet are in a square metre?
One square metre is about 10.764 square feet. To go the other way, divide square feet by 10.764.
How do I measure a room in square metres?
Measure the longest length and width of the floor in metres, at skirting board level, and multiply them. For awkward shapes, split the room into rectangles and add them up.
What's the difference between metres and square metres?
A metre measures length, in one direction. A square metre measures area: a square 1m long and 1m wide.
Measuring properly before you buy saves money and return trips. Use the Square Meter Calculator whenever you're pricing a floor, lawn or patio.
Sources and further reading
- GOV.UK: Weights and measures – the lawgov.uk
- RICS: Code of measuring practicerics.org
- Energy Saving Trust: Home insulationenergysavingtrust.org.uk
Links open official and independent websites in a new tab.
This guide is general information to help you understand your options. It isn't financial, tax, legal or building advice and doesn't take your personal circumstances into account. Figures were checked when the guide was last updated and can change, so confirm anything important with GOV.UK, HMRC, a regulated adviser or a qualified tradesperson.