Square metre calculator
Pick a shape for each room, type its measurements and get the total floor area in square metres, with square feet alongside.
Total floor area
- Total floor area
- 26.4 m²
- Square feet
- 284.17 sq ft
Estimate only. Check the product label and the building regulations where you live before you buy or build.
Quick answer
Square metres are length × width in metres for a rectangular room. For any other floor, split it into rectangles, triangles, circles or trapeziums, work out each part and add them up: a 4.5 × 3.6 m room (16.2 m²) plus a 3.4 × 3 m room (10.2 m²) is 26.4 m². Divide square metres by 0.09290304 to get square feet, so 26.4 m² is 284.17 sq ft.
How to use the square metre calculator
- Choose how you measured: metres, centimetres or millimetres. If your measurements are in feet and inches, switch to Imperial and pick Feet and inches. Numbers you have already typed are converted.
- For each room or part of a room, pick its shape and type the measurements. The drawing shows the shape you entered, and its area appears next to it.
- Add an area for every room or section of floor. Set an area to Subtract for anything you will not cover, such as a chimney breast or a fitted kitchen unit, or to Half (50%) for low storage space under the eaves.
- Read the total in square metres, with square feet below it. An area with a missing measurement is left out of the total until you fill it in.
How do you work out square metres?
Multiply the length by the width, both in metres: a room 4.5 m long and 3.6 m wide is 4.5 × 3.6 = 16.2 m². For a floor that is not a rectangle, split it into simple shapes, work out each one with the formulas below and add the results. Subtract anything you will not cover.
If you measured in centimetres, divide the result by 10,000 to get square metres; in millimetres, divide by 1,000,000. A foot is one third of a yard and a yard is 0.9144 m, so a foot is exactly 0.3048 m and a square foot is exactly 0.09290304 m². One square metre is about 10.764 sq ft.
rectangle = length × widthL-shape = overall length × overall width − missing corner length × missing corner widthtriangle = base × height ÷ 2triangle from sides a, b, c: s = (a + b + c) ÷ 2, area = √(s × (s − a) × (s − b) × (s − c))circle = π × (diameter ÷ 2)²trapezium = (parallel side 1 + parallel side 2) ÷ 2 × distance between themsquare feet = square metres ÷ 0.09290304Square metres and square feet of common room sizes
Each value is length × width, converted with 1 sq ft = 0.09290304 m² and rounded to two decimals.
| Room size (m) | Square metres | Square feet |
|---|---|---|
| 2.4 × 3.0 | 7.20 | 77.50 |
| 3.0 × 3.0 | 9.00 | 96.88 |
| 3.0 × 3.6 | 10.80 | 116.25 |
| 3.6 × 3.6 | 12.96 | 139.50 |
| 3.6 × 4.2 | 15.12 | 162.75 |
| 4.0 × 4.5 | 18.00 | 193.75 |
| 4.5 × 5.0 | 22.50 | 242.19 |
| 5.0 × 6.0 | 30.00 | 322.92 |
| 6.0 × 7.2 | 43.20 | 465.00 |
Worked examples
An L-shaped kitchen-diner
The room is 6 m along its longest wall and 5.2 m across, with a 2.4 m × 2.2 m corner taken up by a utility room. Choose L-shape and enter 6, 5.2, 2.4 and 2.2.
The full rectangle is 6 × 5.2 = 31.2 m² and the missing corner is 2.4 × 2.2 = 5.28 m², so the room is 31.2 − 5.28 = 25.92 m². That is 279 sq ft.
A front room with a bay window and a chimney breast
The room is 4.2 m × 3.6 m, which is 15.12 m². The bay window is a trapezium 2.4 m along the wall, 1.2 m across the front and 0.6 m deep: (2.4 + 1.2) ÷ 2 × 0.6 = 1.08 m². Add it as a second area.
The chimney breast stands 0.4 m out from the wall and is 1.4 m wide, and the new floor will not go under it. Add it as a third area set to Subtract: 0.56 m². The total is 15.12 + 1.08 − 0.56 = 15.64 m², or 168.35 sq ft.
How big does a bedroom have to be in England?
A single bedroom must be at least 7.5 m² and 2.15 m wide, and a double or twin bedroom at least 11.5 m², under the nationally described space standard. It applies to new homes in England where the local planning authority has adopted it in its Local Plan. Whole homes are measured as Gross Internal Area: the floor space between the internal faces of the perimeter walls.
| Room or home | Minimum floor area | Minimum width |
|---|---|---|
| Single bedroom | 7.5 m² | 2.15 m |
| One double or twin bedroom | 11.5 m² | 2.75 m |
| Every other double or twin bedroom | 11.5 m² | 2.55 m |
| 1 bedroom, 2 people, 1 storey | 50 m² | Not set |
| 2 bedrooms, 4 people, 1 storey | 70 m² | Not set |
| 2 bedrooms, 4 people, 2 storeys | 79 m² | Not set |
| 3 bedrooms, 5 people, 2 storeys | 93 m² | Not set |
| 4 bedrooms, 6 people, 2 storeys | 106 m² | Not set |
A built-in wardrobe counts towards the bedroom floor area, but it should not make the room narrower than the minimum width. The standard applies to England only.
Does floor space under a sloping ceiling count?
Not where the headroom is under 1.5 m, unless that space is used only for storage. That is the rule for Gross Internal Area in the nationally described space standard for England. Storage space with 900 to 1500 mm of headroom, such as under the eaves, counts at 50%, and anything lower than 900 mm does not count at all.
To measure a loft this way, enter the part with at least 1.5 m of headroom as an area set to Add. A loft room 5.4 m long and 4.2 m wide, with a 0.7 m strip under the eaves along each long side, has 5.4 × 2.8 = 15.12 m² at full height. If the strips are used only for storage and have 900 to 1500 mm of headroom, add each one as an area of 5.4 × 0.7 = 3.78 m² set to Half (50%): the total becomes 15.12 + 3.78 = 18.9 m². If a strip is not storage, or is lower than 900 mm, leave it out. For a carpet or flooring job, measure every bit of floor you will cover instead.
Questions
How do I work out the square metres of a room?
Multiply the length by the width in metres. A room 4.5 m by 3.6 m is 4.5 × 3.6 = 16.2 m². Measure at floor level from wall to wall, and write each length down as you go. If the room is not a rectangle, split it into rectangles and other simple shapes, work out each one and add them together.
How do I convert square metres to square feet?
Divide square metres by 0.09290304, or multiply by 10.764 for a close answer: 16.2 m² is 174.38 sq ft. The factor is exact because a foot is defined as 0.3048 m. Under the Weights and Measures Act 1985, which covers England, Wales and Scotland, a figure in square feet used in trade is a supplementary indication: it can accompany a metric figure, which must be the more prominent.
How do I work out the area of an L-shaped room?
Multiply the overall length by the overall width, then subtract the missing corner. A room 6 m by 5.2 m with a 2.4 m by 2.2 m corner cut out is 31.2 − 5.28 = 25.92 m². You can also split the L into two rectangles and add them: 3.6 × 5.2 + 2.4 × 3.0 = 18.72 + 7.2 = 25.92 m², the same answer.
How do I measure a bay window?
Treat a splayed bay as a trapezium: the opening along the wall and the front window are the two parallel sides, and the depth is the distance between them. A bay 2.4 m along the wall, 1.2 m across the front and 0.6 m deep is (2.4 + 1.2) ÷ 2 × 0.6 = 1.08 m². Add it to the main room as its own area.
How many square metres is a double bedroom?
At least 11.5 m² under the nationally described space standard, and a single bedroom at least 7.5 m². One double must also be at least 2.75 m wide, and any other double at least 2.55 m. A room 3.6 m by 3.3 m is 11.88 m², so it meets the floor area. The standard applies to new homes in England where the local planning authority has adopted it.
Sources
- legislation.gov.uk (The National Archives), Weights and Measures Act 1985, Schedule 1, Definitions of Units of Measurement (checked 19 October 2026)Yard = 0.9144 metre, foot = 1/3 yard, square foot = 1/9 square yard (Part VI). The page lists a pending change by 2025 c. 20 that is not yet applied to the text.
- legislation.gov.uk (The National Archives), Weights and Measures Act 1985, section 8 (checked 19 October 2026)Section 8(5A): a non-metric figure is a supplementary indication when it accompanies a more prominent metric figure. Extent: England, Wales and Scotland.
- Ministry of Housing, Communities and Local Government (GOV.UK), Technical housing standards: nationally described space standard (checked 19 October 2026)Applies to England where adopted in a Local Plan. Gross Internal Area, minimum floor areas (Table 1), bedroom sizes and widths, the 1.5 m headroom rule and storage at 900 to 1500 mm counted at 50%.
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