Square Metre Calculator
Enter dimensions in metres or centimetres — the area is always shown in m².
Area
12.00 m²
In square feet
129.17 sq ft
A 4.0m × 3.0m rectangle covers 12.00 m² — about 129.17 sq ft in the old scale.
Quick answer
A square metre calculator finds area by multiplying dimensions together: length × width for a rectangle, π × radius² for a circle, or 0.5 × base × height for a triangle. Enter measurements in metres or centimetres and the result always converts to square metres, plus square feet for reference.
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Square Metre Calculator is one of numbers, percentages and conversion tools on OneCalculate — see the full set for this category.
Browse MathsHow it works
This square metre calculator works out area using a different formula depending on the shape you pick, then always reports the result in square metres (m²), no matter which shape or unit you started with.
Rectangle (including most rooms):
Area = Length × WidthA room that’s 4 m long and 3 m wide covers 4 × 3 = 12 m².
Circle:
Area = π × Radius²Where π (pi) is approximately 3.14159. A circle with a 2 m radius covers π × 2² = 12.57 m².
Triangle:
Area = 0.5 × Base × HeightThis uses the perpendicular height — the straight vertical distance from the base to the opposite point, not a sloped side. A triangle with a 5 m base and 3 m height covers 0.5 × 5 × 3 = 7.5 m².
If you measure in centimetres instead of metres, every dimension is divided by 100 before the formula above is applied, so a 480 cm × 350 cm room is treated as 4.8 m × 3.5 m and the area still comes out in square metres — you never need to convert by hand or wonder whether a result is in cm² or m². For reference, this calculator also shows the area converted to square feet (× 10.7639), since some tradies and older building plans still quote coverage that way.
Worked example
Amelia is retiling the main bedroom of her Perth townhouse before putting it on the market and wants to know how much new flooring to order. She measures the room at 4.8 m long and 3.5 m wide.
Area = 4.8 × 3.5 = 16.8 m²
Flooring is almost always sold by the square metre, so Amelia now knows to budget for at least 16.8 m². Tradies commonly add a further 10% on top (about 1.7 m² here) to cover cuts and pattern matching, bringing her order to roughly 18.5 m². Her supplier’s website happens to quote box coverage in square feet as well: 16.8 m² × 10.7639 = 180.83 sq ft, which is the figure she checks against to make sure both numbers agree.
While she has the tape measure out, Amelia also checks a round rug she’s eyeing for the reading nook, which has a 1.2 m radius.
Area = π × 1.2² = π × 1.44 = 4.52 m²
That’s small enough to fit the corner comfortably without crowding the bed. Between the flooring and the rug, Amelia now has the two square-metre figures she needs before pricing up materials — knowing a room’s exact area is the first step before working out how many tiles, litres of paint or metres of skirting board the job actually needs.
| Item | Dimensions | Area |
|---|---|---|
| Bedroom floor | 4.8 m × 3.5 m | 16.80 m² (180.83 sq ft) |
| Round rug | 1.2 m radius | 4.52 m² (48.69 sq ft) |
Frequently asked questions
How do you calculate the square metres of a room?
Measure the room's length and width in metres, then multiply them together — a 4 m by 3 m room is 12 m². For an oddly shaped room, split it into simpler rectangles or triangles, work out each area separately, then add the results together for the total square metreage.
How many square feet are in a square metre?
One square metre equals approximately 10.76 square feet. To convert, multiply your area in square metres by 10.7639 — a 20 m² room, for example, works out to roughly 215.3 square feet. This calculator shows both figures automatically so you never need to convert by hand.
How do you work out the area of an odd-shaped room?
Split the room into simpler shapes you can measure separately, usually rectangles, with a triangle for any angled wall, then calculate each shape's area and add them together. An L-shaped room becomes two rectangles, for instance, while a room with a bay window might need an extra triangle.
What's the formula for the area of a circle in square metres?
Area equals pi, about 3.14159, multiplied by the radius squared. If you only know the diameter, halve it first to get the radius — a circular rug with a 1.2 m radius covers roughly 4.52 square metres, the same formula used for round garden beds and pizzas.
Do I need to measure in metres, or can I use centimetres?
Either works. This calculator accepts measurements in metres or centimetres — just select the matching unit and enter your figures as measured. Choosing centimetres automatically converts each dimension to metres before calculating, so the area shown is always correct in square metres, never mixed units.
How much flooring or paint should I buy based on the square metre result?
Suppliers usually quote flooring, tiles and paint coverage per square metre, so once you know a room's area you can compare it directly against the coverage stated on the product packaging. Tradies commonly add five to ten percent extra to cover cuts, waste and pattern matching in irregular rooms.
Why does the triangle formula use height, not the slanted side length?
The triangle area formula, half of base times height, needs the perpendicular height — the straight vertical distance from the base up to the opposite point — not the length of a sloped or angled side. Using a slanted measurement instead of the true perpendicular height will overstate the area.
Written and verified by Nirbhay Tripathi
Last updated 18 August 2026
All rates on this page are verified againstMath Is Fun — Areaon 18 August 2026. See our methodology for the full update calendar.