How to Calculate Square Footage of a Room (Including L-Shapes and Odd Angles)

Square footage is length times width: measure both sides of a room in feet and multiply them. A room that is 12 feet by 10 feet is 12 × 10 = 120 square feet. For rooms that aren’t a simple rectangle, split the space into rectangles, work out each one, and add them together, that single trick handles L-shaped rooms, alcoves and open-plan spaces. To convert to square metres, multiply the square feet by 0.0929.

The basic formula

Area is length × width, and when both are in feet the answer is in square feet. So a bedroom measuring 12 ft along one wall and 10 ft along the other is:

12 ft × 10 ft = 120 square feet

That’s the whole idea. The only rules are that both measurements must be in the same unit (both feet, or both metres) and that you measure the actual floor, wall to wall.

If your tape reads in feet and inches, convert the inches to a decimal first by dividing by 12. A wall that’s 12 ft 6 in is 12 + (6 ÷ 12) = 12.5 ft. Then multiply as normal.

L-shaped and irregular rooms

Most “hard” rooms aren’t hard at all, they’re just two or three rectangles stuck together. The method never changes:

1. Divide the floor plan into rectangles with straight lines.
2. Measure and calculate each rectangle’s area separately.
3. Add the areas together.

For an L-shaped living room, you might split it into a large 12 × 8 ft rectangle (96 sq ft) and a smaller 4 × 6 ft rectangle (24 sq ft). Total: 96 + 24 = 120 sq ft. For a room with a bay window or alcove, treat the alcove as its own little rectangle and add it on.

Circles, triangles and other shapes

Not everything is a rectangle. The two other formulas worth knowing:

Shape	Formula	Example
Rectangle / square	length × width	12 × 10 = 120 sq ft
Triangle	½ × base × height	½ × 10 × 6 = 30 sq ft
Circle	π × radius²	π × 5² ≈ 78.5 sq ft
Circle (from diameter)	π × (diameter ÷ 2)²	π × (10 ÷ 2)² ≈ 78.5 sq ft

For a circular patio, measure across the middle to get the diameter, halve it for the radius, then square the radius and multiply by π (about 3.14159). A round table area 10 ft across is π × 5² ≈ 78.5 sq ft.

Converting between square feet and square metres

The exact conversion comes from the definition of a foot (0.3048 m), so one square foot is 0.3048² = 0.09290304 square metres:

• Square feet → square metres: multiply by 0.0929
• Square metres → square feet: multiply by 10.764

So that 120 sq ft room is 120 × 0.0929 ≈ 11.15 m². Our square footage calculator shows both units at once so you never have to convert by hand.

How much extra to buy for flooring

The bare square footage is what the room is, but it’s not how much flooring to buy. Cuts, offcuts, mistakes and future repairs all eat material, so add a waste allowance on top:

Flooring type / layout	Typical waste to add
Straight lay (planks, tile)	5-10%
Diagonal or herringbone	15-20%
Highly patterned / many cuts	up to 20%

Multiply your square footage by 1.05-1.20 accordingly, then round up to whole boxes. For 120 sq ft of straight-lay flooring at 10% waste, buy for 120 × 1.10 = 132 sq ft. Keeping a spare box from the same batch is smart for later repairs, since colours shift between production runs.

Square footage and price

Once you have the area, price per square foot lets you compare homes, rentals or materials of very different sizes on a fair basis, it’s total price ÷ area. A $350,000 home of 1,800 sq ft works out to about $194 per square foot. Our cost per square foot calculator does this and shows the per-square-metre figure too.