Calculate area for rectangles, circles, triangles, trapezoids, L-shaped and multiple rooms — with flooring, paint and cost estimates.
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Australia uses the metric system — square metres (m²) for area. However, "square" is an old Australian unit still used informally in real estate (1 square = 9.29 m²). Property floor plans show internal area in m².
| Room | Typical area |
|---|---|
| Main bedroom | 12–16 m² |
| Second bedroom | 9–12 m² |
| Living room | 18–30 m² |
| Kitchen | 10–16 m² |
| Bathroom | 4–8 m² |
| Average 3BR home (total) | 180–220 m² |
| Room | Typical area |
|---|---|
| Primary bedroom | 150–225 sq ft |
| Secondary bedroom | 100–140 sq ft |
| Living room | 250–450 sq ft |
| Kitchen | 150–250 sq ft |
| Bathroom | 40–100 sq ft |
| Average 3BR US home (total) | 1,600–2,200 sq ft |
Set the unit selector above to feet (the default) to work entirely in square feet, or switch to metres for square metres — every result shows both units regardless of which you choose.
Written and reviewed by Mohsin Iqbal · Last reviewed August 2026
Square footage is the area of a space, measured in square feet. A room that's 12 feet long and 10 feet wide has 120 square feet of floor — not because the room is "120 feet" of anything, but because area multiplies two dimensions together, and the result is measured in squared units.
This matters for almost everything involving a room or a block of land: how much flooring to order, how much paint to buy, what a property is worth per square foot, whether furniture will fit. Get the area wrong and every material estimate that depends on it is wrong too.
The method depends on the shape, but every formula reduces to the same idea: multiply the dimensions that define the space, in consistent units, then apply the shape's specific formula.
Area = Length × Width (rectangle)
Area = Side × Side (square)
Area = π × radius² (circle)
The most common mistake is mixing units mid-calculation — measuring one wall in feet and another in inches, then multiplying them directly. Convert everything to the same unit first.
The simplest and most common case. A rectangle's area is length times width; a square is the same formula with both sides equal.
| Room | Dimensions | Area |
|---|---|---|
| Rectangle | 12ft × 10ft | 120 ft² |
| Square | 10ft × 10ft | 100 ft² |
Perimeter — the distance around the edge — is separate from area and is useful for skirting boards, fencing, or edging: 2 × (length + width) for a rectangle, 4 × side for a square.
Triangular spaces — an attic corner, an angled extension — use base and height, not the three side lengths.
Area = 0.5 × Base × Height
The height here is the perpendicular distance from the base to the opposite point, not the length of a slanted side. Measuring along the slope instead of straight up from the base is the usual mistake, and it overstates the height.
Round features — a circular patio, a rug, a garden bed — use the radius (half the diameter) squared, times pi.
Area = π × radius²
Measure the diameter (straight across the middle) rather than trying to estimate the radius directly — it's easier to measure accurately with a tape measure, and this calculator halves it for you.
| Step | Working | Result |
|---|---|---|
| 4m diameter | radius = 4 ÷ 2 | 2m |
| Area | π × 2² | 12.57 m² |
A trapezoid has two parallel sides of different lengths — common in angled extensions or non-rectangular blocks of land.
Area = 0.5 × (Side A + Side B) × Height
Here, height means the perpendicular distance between the two parallel sides, not a diagonal measurement.
| Step | Working | Result |
|---|---|---|
| Side A | 5m | — |
| Side B | 7m | — |
| Height | 4m | — |
| Area | 0.5 × (5 + 7) × 4 | 24 m² |
An L-shaped room is measured as two separate rectangles, then added together — which matches how people actually measure one in practice: two tape-measure rectangles, not a single complex shape.
| Section | Dimensions | Area |
|---|---|---|
| Rectangle A | 6m × 4m | 24 m² |
| Rectangle B | 3m × 2m | 6 m² |
| Total | — | 30 m² |
Split the room at its inside corner into the two rectangles that make it up, measure each independently, and add. This works for any L-shape regardless of which way it turns.
For a whole floor or a whole house, add each room's individual area rather than trying to measure the outside perimeter and guess at internal walls. Internal walls, built-ins and stairwells all reduce usable floor area, so room-by-room measurement is more accurate than one large outer measurement.
| Room | Dimensions | Area |
|---|---|---|
| Living Room | 6m × 5m | 30.00 m² |
| Master Bedroom | 4m × 4m | 16.00 m² |
| Kitchen | 4m × 3m | 12.00 m² |
| Bathroom | 2.5m × 2m | 5.00 m² |
| Total | — | 63.00 m² (678.13 ft²) |
This is roughly the floor plan of a modest three-bedroom home — without hallways, laundry, garage or outdoor areas, which is why a full house often measures noticeably larger once every space is added. Add up to 20 rooms in the calculator above and it totals them the same way.
All of these are ordered by area, with a waste allowance added for cuts, offcuts and mistakes. 10% waste is standard for a simple rectangular room; increase to 15% for rooms with lots of corners, angles, or a diagonal laying pattern that wastes more material.
Paint coverage is measured in square metres per litre, and it depends heavily on the surface. Australian interior paints commonly cover in this range:
| Surface | Typical coverage (per litre, per coat) |
|---|---|
| Smooth, previously painted wall | 12–16 m² |
| New plaster or bare surface | 8–10 m² |
| Textured or rough render | 6–10 m² |
Most interior jobs use two coats. This calculator works out wall area from perimeter × wall height (minus doors and windows), not floor area — for a 10m × 8m room with a 2.4m wall height, that's a 36m perimeter × 2.4m = 86.4 m² of gross wall area; at 14 m² per litre over two coats, that's 86.4 × 2 ÷ 14 ≈ 12.3 litres. No separate waste allowance is added for paint — round up to your product's next full tin. Check the coverage rate printed on your specific paint tin — it varies by brand and finish, and this calculator lets you enter the exact figure from your product.
Larger areas — blocks of land, paddocks, parks — are usually expressed in acres or hectares rather than square metres, since the numbers stay manageable.
| Unit | Equals |
|---|---|
| 1 acre | 4,046.86 m² |
| 1 hectare | 10,000 m² (2.471 acres) |
| Typical Australian residential block | ~400–700 m² |
| Country | Everyday unit | Land/large areas |
|---|---|---|
| Australia | Square metres (m²) | Hectares, square metres |
| United States | Square feet (ft²) | Acres |
| Canada | Square feet (residential real estate), square metres (elsewhere) | Acres, hectares |
| United Kingdom | Square feet and square metres both common | Acres, hectares |
Australia moved to metric in the 1970s, so square metres dominate everyday use, though older properties and some trades still reference imperial figures. The US remains almost entirely imperial for residential measurement. The UK and Canada sit in between, with both systems in active use depending on context.
Acres and hectares are easy to lose intuition for, since most people don't walk a whole acre regularly. A useful anchor: a FIFA-standard soccer pitch (105m × 68m) is 7,140 m², or 0.714 hectares — close enough to one hectare that it works as a mental benchmark. A standard suburban Australian block at 500–600 m² is a small fraction of that, well under a tenth of a hectare. A one-acre rural block, at just over 4,000 m², is roughly seven or eight standard suburban blocks combined.
Australian building and real estate uses square metres exclusively for area, governed by measurement standards under the Property Council of Australia's Method of Measurement for residential and commercial space. Land size on a title is always in square metres or hectares.
US residential real estate is measured in square feet, and "square footage" in a property listing typically means finished, heated living space — garages, unfinished basements and porches are usually excluded or listed separately. Land is measured in acres.
UK property listings have shifted toward square metres in recent years, following RICS (Royal Institution of Chartered Surveyors) guidance, though square feet still appears widely, particularly for older listings and in casual conversation.
Canadian residential real estate predominantly uses square feet, following the Canadian standard method of measurement, while trades and construction documentation frequently work in metric. It's common to see both units quoted side by side in a property listing.
Commercial leasing often distinguishes gross floor area (everything within the external walls) from net lettable area (the space a tenant actually occupies, excluding shared corridors, lift wells and plant rooms). Residential figures are usually simpler — the finished living area, without that gross/net distinction, though garages and outdoor areas are typically listed separately.
Multiply length by width for a rectangular room, in consistent units. For a 12ft by 10ft room, that's 12 × 10 = 120 square feet. Other shapes use their own formula — this calculator handles rectangles, squares, circles, triangles, trapezoids and L-shaped rooms.
1 square metre equals approximately 10.764 square feet. To convert square metres to square feet, multiply by 10.764; to go the other way, divide by 10.764.
Split it into simpler shapes — rectangles, triangles or trapezoids — measure each one, and add the areas together. This calculator's L-shaped room mode does exactly this for the most common irregular layout, treating it as two rectangles.
Calculate the room's area, then add a waste allowance — typically 10% for a simple rectangular room, 15% for rooms with more corners or a diagonal laying pattern. Check the coverage printed on your specific flooring product to work out how many boxes that area requires.
Take the wall area (perimeter × wall height, minus doors and windows), multiply by the number of coats (usually 2), and divide by the paint's coverage rate. Australian interior paints typically cover 12–16 m² per litre on a smooth wall. A 10m × 8m room with a 2.4m wall height has 86.4 m² of gross wall area, so at 14 m²/L over two coats that's about 12.3 litres. This calculator doesn't add a separate waste allowance for paint — round up to your product's next full tin.
By multiplying the dimensions that define a shape's area — length and width for a rectangle, base and height for a triangle, and so on. Each shape has its own formula, but all of them produce an area in squared units from linear measurements.
Area is the amount of surface a shape covers, in squared units. Perimeter is the total distance around its edge, in linear units. A 10m × 2m room and a 5m × 4m room have the same 20m² area but different perimeters — 24m versus 18m — because they're shaped differently.
Divide by 10.764. A 1,000 square foot area is roughly 92.9 square metres. To go the other way, multiply square metres by 10.764 to get square feet.
Room by room, then summed — internal walls, built-ins and stairwells reduce usable floor space compared to the building's outer footprint, so measuring each room individually is more accurate than measuring the perimeter and assuming it's all usable area.
Yes — the Multiple Rooms mode lets you add up to 20 rooms with their own length and width, and totals the area automatically, showing each room's contribution to the total.
Gross floor area is everything within a building's external walls. Net lettable area, used mainly in commercial leasing, excludes shared spaces like corridors, lift wells and plant rooms — it's the space a tenant actually occupies and pays for.
Multiply the lawn area by the sowing rate on your seed packet — commonly around 35g per m² for a new lawn, though it varies by grass species. A 100 m² lawn at 35g/m² needs about 3.5kg of seed.
Area alone tells you the footprint, but ordering concrete needs volume — area multiplied by thickness. Calculate the area here, then use the Concrete Calculator with that figure and your slab thickness to get cubic metres, bags and cost.
Listed square footage often follows a specific standard (finished living area in the US, for example) that excludes garages, porches or unfinished spaces — while a DIY measurement might include areas the standard excludes, or measure at skirting height rather than usable floor level.
Roughly 400–700 m² for a standard suburban block, though this varies enormously by city and by how recently the land was subdivided — inner-city blocks are often much smaller, and outer-growth-corridor blocks can be larger or smaller depending on the estate.
Measure the length and width of the room in feet, then multiply them together. A 12ft × 11ft bedroom is 132 sq ft. For rooms that aren't a simple rectangle, split them into rectangles, triangles or use the L-Shaped Room mode above and the calculator adds the pieces together for you.
US real estate listings generally follow the ANSI Z765 standard, counting finished, heated living area only — garages, unfinished basements, porches and sheds are excluded even though they're part of the building. That's the most common reason a DIY room-by-room measurement comes out higher than the number on a listing.