Square Footage Calculator

Enter both measurements in feet. The calculator multiplies them for the area in square feet, then converts it three ways:

• Square yards: square feet ÷ 9
• Square meters: square feet × 0.092903
• Acres: square feet ÷ 43,560

The default 20 ft × 15 ft room is 300 sq ft, 33.33 sq yd and 27.87 sq m. Every result is rounded to two decimal places, so the acres line shows 0 or 0.01 for most rooms. It becomes useful for lots and yards: a 120 ft × 250 ft lot is 30,000 sq ft, or 0.69 acres.

The boxes take decimal feet, so inches have to be divided by 12 first. This is the most common source of error, because 12 ft 4 in is not 12.4 ft.

A 12 ft 4 in × 10 ft room entered as 12.33 × 10 gives 123.33 sq ft. Typed as 12.4 × 10, it gives 124. The arrow buttons move in half-foot steps, but you can type any decimal.

If you measured in meters, multiply each side by 3.28084 first. A 4.2 m × 3.6 m room is 13.78 ft × 11.81 ft, or 162.75 sq ft, and the square meters line then shows the 15.12 you started with.

• L-shaped rooms: split them into two rectangles, run each one and add. A 14 × 12 main area with an 8 × 6 alcove is 168 + 48 = 216 sq ft.
• Cut-outs: subtract what you won't cover. A 22 × 12 kitchen with a 3 × 4 island is 264 − 12 = 252 sq ft of floor.
• Triangles: run the two sides that meet at the right angle, then halve the result.
• Circles: use π × radius². A round patio 10 ft across has a 5 ft radius and covers 78.54 sq ft.

Flooring is usually sold by the box, with the coverage printed on it. Divide your area by that coverage and round up to whole boxes. 216 sq ft with boxes covering 22 sq ft needs 9.82, so buy 10, plus whatever extra the product's instructions suggest for cuts and waste.

Carpet is sometimes priced per square yard, which is why that line is there: 300 sq ft is 33.33 sq yd.

Paint needs wall area, not floor area. Enter the room's perimeter as the length and the ceiling height as the width. The 20 × 15 room has a 70 ft perimeter, and with 8 ft walls that is 560 sq ft of wall before you subtract doors and windows.