Show the formula and working
This free square metre calculator works out the area of a room, floor, wall or garden in square metres and square feet, for homeowners and renters in the UK, Ireland and Europe planning flooring, paint, turf or a quote. It handles rectangles, circles and triangles, adds an allowance for cutting and waste, and gives an estimated cost from your own price per m².
Quick answer: A square metre calculator multiplies length by width in metres. A room 4 m long and 3.5 m wide is 4 x 3.5 = 14 m², which is 150.7 ft². For a circle use 3.1416 x radius squared, and for a triangle use base x height / 2. Add about 10% extra when buying flooring.
What Is a Square Metre Calculator?
A square metre calculator is a tool that measures a flat surface in square metres (m²), the metric unit of area equal to a square 1 m on each side. It turns your measurements into the figure that flooring, paint, tiles and turf are priced by.
The formula in plain words: for a rectangle or square, multiply the length by the width. For a circle, halve the diameter to get the radius, square it and multiply by pi (3.1416). For a triangle, multiply the base by the height and halve the answer. Multiply by the number of identical areas, then add your extra percentage. To convert to square feet, divide square metres by 0.09290304, because one foot is exactly 0.3048 m, a third of the 0.9144 m yard defined by NIST.
How Do You Use the Square Metre Calculator?
- Pick the Shape: “Rectangle or square”, “Circle” or “Triangle”. Use the imperial switch if you measured in feet.
- Enter the Length. For a circle this is the diameter, and for a triangle it is the base.
- Enter the Width. For a triangle this is the height at right angles to the base. A circle does not need it.
- Set the Number of identical areas if you have several the same, such as two matching bedrooms.
- Set Extra for cutting and waste, for example 10% for flooring, or 0% for an exact area.
- Optionally type a Price per m² from your quote, or 0 to hide the cost.
- Read the result and open “Show the formula and working” to see each multiplication and the square feet conversion.
How Do You Work Out Square Metres From Centimetres?
Divide each measurement in centimetres by 100 to get metres, then multiply them: 350 cm by 280 cm becomes 3.5 m x 2.8 m = 9.8 m². If you have already multiplied the centimetres, divide the answer by 10,000, because one square metre holds 100 x 100 = 10,000 cm². Mixing centimetres and metres is the most common reason a result is out by a factor of 100.
How Do You Convert Square Feet to Square Metres?
Multiply square feet by 0.0929 to get square metres, or divide square metres by 0.0929 to get square feet. One square metre is about 10.76 ft², so a 150 ft² bedroom is 13.9 m². Never convert a length and then square it by eye: convert the area, or convert both sides first and then multiply. The imperial switch in the tool does this for you.
How Big Should a Room Be in Square Metres?
In England, a new single bedroom should be at least 7.5 m² and a double at least 11.5 m², under the government’s Nationally Described Space Standard. The same standard sets minimum floor areas for whole homes, such as 50 m² for a one bedroom flat for two people. Councils use it for new homes, so it is a useful yardstick when comparing listings that quote square metres.
| Space | Minimum area | Minimum width | In square feet |
|---|---|---|---|
| Single bedroom | 7.5 m² | 2.15 m | 80.7 ft² |
| Double or twin bedroom | 11.5 m² | 2.75 m (main), 2.55 m (others) | 123.8 ft² |
| 1 bedroom, 1 person home (one storey) | 39 m² | 419.8 ft² | |
| 1 bedroom, 2 person home (one storey) | 50 m² | 538.2 ft² | |
| 2 bedroom, 4 person home (one storey) | 70 m² | 753.5 ft² | |
| 3 bedroom, 5 person home (two storey) | 93 m² | 1,001 ft² |
Areas with headroom below 1.5 m do not count towards the floor area under the standard, unless used only for storage, which matters in loft rooms.
How Much Extra Should You Add to Square Metres?
Add extra only for materials that are cut to fit: the tool uses 10% as an editable example for flooring and tiles. Follow the allowance on your product’s instructions, and add more for diagonal or patterned layouts with many cuts. Paint is different: it is worked out from wall area and coverage per litre, so the paint calculator handles doors, windows and coats for you, and the laminate flooring calculator turns square metres into packs.
Worked Example: Flooring a Bedroom
Example: new flooring is going into a bedroom 4 m long and 3.5 m wide. Keep the shape as “Rectangle or square”, enter 4 and 3.5, leave one area, set 10% extra and type the quote of £20 per m² (an example price).
- Area: 4 m x 3.5 m = 14 m², which is 150.7 ft².
- Area to buy: 14 m² x 1.10 = 15.4 m².
- Estimated cost: 15.4 m² x £20 = £308.00.
The room is above the 11.5 m² minimum for a double bedroom in the space standard. More tools for floors are on the flooring calculators page.
Square Metre Calculator FAQs
How do I calculate square metres of a room?
Measure the length and width of the floor in metres and multiply them. A room 5 m by 4 m is 20 m². For an L-shaped room, split it into rectangles, work out each one and add them together.
How many square feet are in a square metre?
One square metre is 10.7639 ft². That follows from the exact definition of the foot as 0.3048 m, so one square foot is 0.09290304 m². For quick estimates, multiply square metres by 10.76.
Is m² the same as square metres?
Yes. The symbol m² and the words square metres mean the same unit of area. Some people write sq m or sqm. It is not the same as metres squared of a length, so 3 m² is not a square 3 m on each side, which would be 9 m².
How do I measure a room accurately?
Measure wall to wall at floor level with a tape or laser measure, and take two readings on each side because walls are rarely perfectly straight. Use the larger figure when buying materials, and include door recesses and bay windows.
What is the area of a circle in square metres?
Multiply 3.1416 by the radius squared, where the radius is half the diameter. A round patio 3 m across has a radius of 1.5 m, so the area is 3.1416 x 1.5 x 1.5 = 7.07 m².
How much does a square metre of flooring cost?
Prices vary widely by material, quality and region, so this tool does not assume one. Type the price per m² from your supplier or fitter, and the tool multiplies it by the area including your waste allowance to give a total.
Checked October 2026. Sources: NIST, SI units of length, GOV.UK, Technical housing standards: nationally described space standard, Wikipedia, Square metre.