How to Calculate Square Footage
No black box: here are the exact formulas this site uses, how to measure a room step by step, and how to handle L-shaped rooms, circles, triangles and unit conversions.
Step 1: Measure the room
You need three things: a tape measure (or laser measure), a pencil, and a rough sketch of the floor. Sketch first, then measure each wall and write the number straight onto the sketch. Measure along the floor or at skirting-board level, wall to wall, and if a wall is partly blocked by furniture, measure above it at the same distance from the corner.
Measure every wall β do not assume opposite walls are equal. In older houses they often differ by an inch or two; for a simple rectangle use the longer measurement for ordering materials.
Step 2: Rectangles β length Γ width
Area = length Γ width
Example β a 12 ft Γ 12 ft bedroom: 12 Γ 12 = 144.00 sq ft. The same formula works for a whole floor, a garden, a driveway or a single tile β if it is a rectangle (or can be split into rectangles), length times width is all you need.
Step 3: L-shaped and awkward rooms β split and add
An L-shape is two rectangles wearing a trench coat. Split it where the L bends, calculate both parts, and add them:
(16 ft Γ 12 ft) + (6 ft Γ 8 ft) = 192 + 48 = 240.00 sq ft
The calculator on our home page does this for you β one row per rectangle, totalled automatically. The same split-and-add idea handles rooms with alcoves, bay windows and chimney breasts.
Step 4: Circles and triangles
Circle: area = Ο Γ radiusΒ² Β Β·Β Triangle: area = base Γ height Γ· 2
The radius is the distance from the centre of the circle to its edge β half the diameter. If you measured across the whole circle (the diameter), halve it first. A round patio with a 10 ft radius is Ο Γ 10Β² = 314.16 sq ft.
For a triangle, the height must be measured at a right angle to the base. A triangular garden bed with a 10 ft base and 8 ft height is 10 Γ 8 Γ· 2 = 40.00 sq ft.
Step 5: Convert between sq ft, sq m and sq yd
sq ft β sq m: multiply by 0.092903 Β Β·Β sq m β sq ft: multiply by 10.7639 Β Β·Β sq ft β sq yd: divide by 9
So the 12 Γ 12 room is 144.00 sq ft = 13.38 sq m = 16.00 sq yd. Going the other way, a room listed as 12 sq m is 129.17 sq ft. Flooring is often sold by the square metre in Europe and by the square foot in North America, so this conversion comes up constantly β every result on this site shows all three units.
Step 6: Add waste, then price it
The bare area is the minimum material that ends up on the floor β but cuts, breakage and pattern matching use more. The standard allowance is 10% (15% for diagonal layouts). Our example room: 144.00 sq ft + 10% = 158.40 sq ft to order. At $5 per square foot that is $792.00 of material, versus $720.00 for the bare area β the difference is the cuts.
Always round up to whole boxes or packs when you order: materials are sold in fixed pack sizes, and a matching spare box is worth having if a piece is ever damaged.