Square Footage Calculator
Enter length and width in feet to calculate the square feet of a room, wall, deck, or lot. Repeat identical areas, subtract doors and windows, add a waste allowance, and convert the total to square yards and square meters.
Measure an area in square feet
How this tool turns dimensions into area
Area in the imperial system is refreshingly literal: measure two sides in feet, multiply them, and the answer is already in square feet. Where estimates go wrong is everything around that multiplication β inches left unconverted, rooms that are not true rectangles, and openings nobody deducted. The square feet calculator above handles all three in one pass.
Enter the two sides and you get the gross area. Add a count when several surfaces share the same dimensions, which is how most people measure walls: a 12 ft by 8 ft wall entered four times gives 384 sq ft of paintable surface before doors come out. Then subtract the openings β roughly 21 sq ft for a standard door, 15 sq ft for an average window β and what remains is the number you take to the store.
Odd shapes, wall area and unit conversions
Almost no real room is a clean rectangle, and you do not need a different formula for the ones that are not. Split an L-shaped space into two rectangles, run each through the tool, and add the results. Bay windows, closets, and alcoves get their own small rectangle. Circles are the one exception: use Ο Γ radiusΒ², where the radius is measured in feet.
The results also convert. Nine square feet make one square yard, which is how carpet is still quoted in parts of the US, and one square foot is 0.0929 square meters, which is what you need when a product sheet is metric. Flooring, tile, and paint are all sold against these three units, so the tool prints them together rather than making you convert twice.
How to use this calculator
- Measure length and width in feet. Run a tape along the two sides of the surface and record both in feet, converting inches to decimals β 14 ft 9 in becomes 14.75. Measure at floor level, not along baseboards, and take the longest dimension of each side.
- How to calculate square feet for one rectangle. Multiply the two sides together. A 16 ft by 12 ft room is 16 Γ 12 = 192 sq ft. Both numbers have to be in feet before you multiply β mixing feet and inches is the single most common source of a wrong material order.
- Repeat the area and subtract openings. Break odd rooms into rectangles and enter them one at a time, or use the count field for identical surfaces such as four walls at the same height. Then deduct doorways and windows so you are not paying for material that covers nothing.
- How to calculate square footage with a waste allowance. Add 10% on top of the net area for offcuts, mistakes, and future repairs, or 15% for diagonal and herringbone layouts where the cuts are less forgiving. The tool shows both the net and the padded figure.
Frequently asked questions
How do you calculate square feet in an L-shaped room?
Split it into two rectangles, measure each one, and add the two results. There is no separate formula for an L β it is always two rectangles that share an edge.
Does this square feet calculator work for walls and ceilings?
Yes. For a wall, enter the wall length and the ceiling height; for a ceiling, use the same footprint as the floor. Set the count field to the number of walls that share those dimensions.
How many square feet are in a square yard?
Exactly nine, because a square yard is 3 ft by 3 ft. Carpet is often priced per square yard, so divide your total by 9 before comparing a carpet quote to a hardwood quote.
Should closets and hallways count toward a home's living area?
For flooring, yes β you have to cover them. For a real estate listing, the ANSI Z765 measuring standard counts finished, heated space with a ceiling of at least 7 ft, which excludes most garages and unfinished basements.
How much waste should I add for flooring in 2026?
Ten percent is the 2026 industry default for a straight lay in a simple rectangular room, and 15% for diagonal, herringbone, or heavily cut-up floor plans. Keep the offcuts for future repairs.
Typical spaces and their area
| Space | Dimensions | Area | Square yards |
|---|---|---|---|
| Small bedroom | 10 Γ 10 ft | 100 sq ft | 11.1 sq yd |
| Living room | 16 Γ 20 ft | 320 sq ft | 35.6 sq yd |
| Two-car garage | 20 Γ 20 ft | 400 sq ft | 44.4 sq yd |
| Backyard deck | 12 Γ 16 ft | 192 sq ft | 21.3 sq yd |
Flooring boxes typically cover 20 to 25 sq ft each, so a 320 sq ft living room with 10% waste works out to roughly 15 boxes. Interior paint covers about 350 to 400 sq ft per gallon per coat.