Square Meter Calculator
A 20 m² area comes from length × width in metres — a 4 m × 5 m room is 20 m². Add a row per room or shape (rectangle, L-shape, circle, triangle) for a running total, then add a waste % (10% is standard, 15–20% for a diagonal or patterned lay) and a pack coverage in m² to get the number of packs to buy — the calculator rounds up automatically.
- Area = length × width: 4 m × 5 m = 20 m²
20 m² total area
215.28 sq ft · 23.92 sq yd · 31,000 sq in · 0.002 ha
With 10% waste: 22 m² required
| Square metres | 20 m² |
| Square feet | 215.278 sq ft |
| Square yards | 23.92 sq yd |
| Square inches | 31,000 sq in |
| Acres | 0.00494 acres |
| Hectares | 0.002 ha |
Area uses standard geometry (rectangle L×W, circle πr², triangle ½·b·h, L-shape = two summed rectangles); every dimension is converted to metres with exact NIST factors (1 ft = 0.3048 m, 1 in = 0.0254 m) before multiplying. 1 sq ft = 0.09290304 m² exactly. How we calculate →
The formula, and how mixed units work
For a rectangular room, area is simply length × width with both sides in the same unit. A room that is 4 m by 5 m is 4 × 5 = 20 m². Every dimension above has its own unit dropdown (mm, cm, m, ft, in), so you can enter one side in centimetres and the other in metres — for example 400 cm × 5 m still comes out at 20 m², because each side is converted to metres before it's multiplied, not after.
The calculator updates live as you type. There's no Calculate button, and the running total at the top adds every row you've entered — one row per room, or one row per shape within an irregular room.
L-shaped rooms: split into two rectangles
Most rooms aren't a single neat rectangle. The reliable method — the one UK flooring retailers teach — is to split the space into two rectangles and add the areas. Pick “L-shape” and enter both rectangles: a 4 m × 5 m main room plus a 2 m × 3 m alcove is (4 × 5) + (2 × 3) = 20 + 6 = 26 m².
The same decomposition handles any irregular shape: a bay window is a rectangle plus a triangle or a half-circle, a landing-plus-alcove is two rectangles. Add one row per part and read the total.
Waste percentage and how you lay the floor
Flooring, tiling and carpet are never bought at the exact measured area — offcuts, mistakes and pattern-matching all use extra material. A 10% waste allowance is the standard default for a straightforward, straight-laid room. For a diagonal lay, a herringbone pattern, or a room with a lot of cuts (alcoves, chimney breasts, doorways), UK trade guidance typically recommends 15–20% instead. Enter your area and the waste % field adds that percentage on top: 20 m² with 10% waste needs 22 m² of material.
The packs calculation: from 22 m² to 10 packs
Knowing the area in m² is only step one — most people buying flooring, tiles or turf actually need to know how many packs or boxes to order. Enter the coverage per pack in m² (check the product label) and the calculator divides your waste-adjusted area by it, then rounds up to the next whole pack — you can't buy a fraction of a box. Worked example: a 20 m² room with 10% waste needs 22 m² of flooring; at 2.2 m² per pack, that's 22 ÷ 2.2 = 10 packs exactly. If the room were slightly bigger — say 22.1 m² needed — the same 2.2 m²-per-pack coverage would round up to 11 packs, not 10.05.
This end-to-end step (area → waste → packs) is the part most generic area calculators skip: they stop at the raw m² figure and leave the purchasing maths to you.
Square metres to square feet, and back
The conversion factors are exact, not rounded approximations: 1 square foot = 0.09290304 m² exactly, a direct consequence of the internationally defined foot (1 ft = 0.3048 m exactly). So a 500 sq ft area — the kind of figure you'll see on a US or older UK property listing — converts to 500 × 0.09290304 = 46.45 m². Going the other way, divide square metres by 0.09290304 (or multiply by roughly 10.764) to get square feet. The calculator shows m², sq ft, sq yd, sq in, acres and hectares for every total simultaneously, so you never need to look up a factor.
m² ↔ sq ft quick-reference table
| Square metres | Square feet |
|---|---|
| 10 m² | 107.6 sq ft |
| 15 m² | 161.5 sq ft |
| 20 m² | 215.3 sq ft |
| 25 m² | 269.1 sq ft |
| 30 m² | 322.9 sq ft |
| 50 m² | 538.2 sq ft |
| 100 m² | 1076.4 sq ft |
Frequently asked questions
Are square metres and metres the same?
No — a metre (m) measures length or distance in one direction; a square metre (m²) measures area, the amount of surface a two-dimensional space covers. A 1 m × 1 m square has an area of 1 m².
What does 1 square metre look like?
It's the area of a square with sides 1 metre long — roughly the size of a small kitchen table, or slightly bigger than a standard door laid flat.
How many square metres is a 10×10 room?
If those measurements are metres, a 10 m × 10 m room is 100 m². If they're feet, convert first: 10 ft × 10 ft = 100 sq ft = 100 × 0.09290304 ≈ 9.29 m². Always check which unit your measurements are in — the calculator above lets you set the unit per side.
What does 'per square metre' mean?
It's a price or rate that applies to each square metre of area — for example, £25 per m² flooring on a 20 m² room costs 20 × £25 = £500 before waste. Enter your price per m² above for an instant material-cost estimate.
How do I convert square feet to square metres?
Multiply the square-foot figure by 0.09290304 (the exact NIST-derived factor). 500 sq ft × 0.09290304 = 46.45 m². To go the other way, divide square metres by the same factor, or multiply by about 10.764.
What is the area of a 5 m by 2 m garden?
5 m × 2 m = 10 m². The same rectangle formula applies to gardens, patios and decking as it does to rooms.
How do I measure the square metre area of a rectangular room?
Measure the length and width in the same unit (usually metres) at floor level, then multiply them. A 4 m × 5 m room is 20 m². Enter the two measurements above and the calculator does the multiplication and unit conversion for you.
How many square metres is a standard UK room?
It varies widely by room type and property age, but as a rough guide UK bedrooms are commonly in the 10–15 m² range and living rooms 15–20 m², based on how UK flooring retailers describe typical room sizes. Always measure your own room rather than relying on an average — enter your real dimensions above.
Do I need to subtract the area for doors and windows?
For flooring and carpet, no — you measure the floor area regardless of doors. For wall coverage (paint, wallpaper, tiling), yes: measure the full wall area first, then subtract door and window openings, or simply add a larger waste % to cover the difference roughly.
How accurate does my measurement need to be?
Measure to the nearest centimetre where possible, and always measure the longest point of an irregular wall or floor. Small errors matter less once you add a 10% (or higher) waste allowance, which is designed to absorb minor measuring imprecision as well as offcuts.
Can I use this calculator for walls and ceilings?
Yes — treat a wall as a rectangle (width × height) or, for a room, add one row per wall and one for the ceiling (length × width), then sum them. Remember to subtract door/window area separately if you need a precise paint quantity.
What's the difference between m2 and m^2 (typed vs superscript)?
None mathematically — 'm2', 'm^2' and 'm²' are all ways of writing “square metres” depending on what characters are available; the superscript ² is just the typographically correct form.
How many tiles do I need per square metre?
It depends on tile size: a 300 mm × 300 mm (0.09 m²) tile needs about 11 tiles per m² before waste; a 600 mm × 600 mm (0.36 m²) tile needs about 3 per m². For flooring bought in packs rather than loose tiles, use the pack-coverage field above (m² per pack) and the calculator rounds up to the number of packs directly.
What is a square metre exactly?
A square metre is the SI (metric) unit of area — the area enclosed by a square with 1-metre sides. It's the standard unit for room, land and material-coverage measurements across the UK and most of the world.
When do you use square metres instead of running metres?
Running (linear) metres measure length only — used for skirting board, timber lengths or fencing runs. Square metres measure a two-dimensional area — used for flooring, tiling, turf, paint and carpet, where you're covering a surface rather than running along an edge.
How do L-shaped or irregular rooms work with this calculator?
Pick the L-shape option and enter both rectangles that make up the room; the calculator adds their areas automatically. For more complex shapes, add extra rows (one per rectangle, circle or triangle section) and use the running total.
Converting from a US or imperial listing? See the square footage calculator for the same multi-room builder in feet and inches.
Researched & verified by the Calcuris Data & Research Team. How we build and check our tools →