Square Footage Calculator

How to measure square footage

Square footage is the floor area of a space: how many one-foot-by-one-foot squares would cover it. For a plain rectangular room you multiply the length by the width. Most homes aren’t one neat rectangle, so the practical method is to split the floor into simple shapes, work out each one and add them up.

1. Sketch the floor and divide it into rectangles, triangles and circles (an L-shaped room is two rectangles).
2. Measure each section wall to wall, in feet and inches or in meters.
3. Enter each section above. The calculator converts inches to decimal feet and adds the sections together.
4. Add a price and a waste allowance if you are buying flooring, tile or other material by the square foot.

The result is shown in both square feet and square meters, so you can compare quotes or product labels in either unit. This calculator starts from measurements; if you already have an area and only need a different unit, the area converter is quicker.

Area formulas

height

for a triangle, the perpendicular distance from the base to the opposite corner, not the sloping side

A, B

the two rectangles an L-shape splits into; measure them so they don’t overlap

Feet and inches become decimal feet first (10 ft 6 in = 10.5 ft). Square feet convert to square meters with the exact factor 0.09290304, which follows from the international foot of exactly 0.3048 m (0.3048² = 0.09290304). A square yard is 9 square feet.

Worked example

A living room of 15 ft × 12 ft and a hallway of 10 ft 6 in × 8 ft (the calculator’s starting values in feet):

1. Living room: 15 × 12 = 180 ft²
2. Hallway: 10 ft 6 in = 10.5 ft, so 10.5 × 8 = 84 ft²
3. Total: 180 + 84 = 264 ft², which is 264 × 0.09290304 = 24.53 m² or 29.33 yd²

With a 10% waste allowance you would buy 264 × 1.10 = 290.4 ft². At $4.50 per square foot that is about $1,306.80.

In meters, a 5 m × 4 m room plus a 3 m × 2.5 m hallway gives 20 + 7.5 = 27.5 m², about 296.01 ft². A round patio 10 ft across covers π × 10² ÷ 4 ≈ 78.54 ft².

Tips for accurate numbers

• Subtract what you won’t cover. For flooring, fixed cabinets or a kitchen island take floor away. Enter the room as an L-shape, or work out the obstruction separately and subtract it.
• Waste depends on the job. Straight plank or tile layouts need less extra than diagonal or herringbone patterns, and small, irregular rooms need more. 5–10% is a common starting allowance; the product’s installation guide is the better authority.
• Buy whole boxes. Flooring is sold by the box or roll. Divide the area to buy by the coverage per box and round up.
• Listed home size is measured differently. A home’s advertised square footage follows the measuring rules of the appraiser or local market (for example, whether wall thickness, stairs or unfinished space count), so adding up room sizes will usually give a smaller figure.