How do I calculate the square footage of an L-shaped room?

Split the L into two rectangles that do not overlap, find each area (length × width) and add them. A room that is 20 × 12 ft with a 8 × 6 ft nook is 240 + 48 = 288 sq ft. In the calculator, pick the L-shape and enter both parts, or add each rectangle as its own room.

Does the square footage of a house include the garage or an unfinished basement?

Not in the finished living area. Under ANSI Z765-2021, which Fannie Mae has required appraisers to use since 2022, garages and unfinished areas are reported separately, and finished space below grade is reported apart from above-grade space. A finished room also needs a ceiling of at least 7 ft to count.

How much extra flooring should I order?

Add about 5 % for planks laid straight, around 10 % for tile, and 10–15 % for diagonal or herringbone layouts, which waste more at the edges. Flooring makers also suggest keeping one or two spare boxes from the same lot for future repairs.

How many square feet is a 10×10 room?

100 square feet (9.29 m²). With 10 % extra for waste you would buy about 110 sq ft of flooring. A 12×12 room is 144 sq ft and a 12×14 room is 168 sq ft; the table of common room sizes on this page lists more.

How do I convert square feet to square meters?

Multiply by 0.09290304. That factor is exact, because a foot is defined as exactly 0.3048 m (NIST). For a quick estimate, divide square feet by 10.76: 168 sq ft ÷ 10.76 ≈ 15.6 m².

Should I measure from the inside or the outside of the walls?

Inside the walls, wall to wall, when you are buying flooring, paint or carpet — that is the surface you will cover. Appraisers measuring a whole house under ANSI Z765 use exterior dimensions instead, which is why a listing's square footage is larger than the sum of the rooms.

Square Footage Calculator — Multiple Rooms & Waste

How to calculate square footage

For a rectangular room, multiply the length by the width. Both measurements must be in feet; the result is in square feet.

Measure the length of the room wall to wall, at floor level, in feet and inches.
Measure the width the same way.
Convert inches to feet — divide by 12 (6 in = 0.5 ft) — or simply type 12'6" into the calculator.
Multiply: 12.5 ft × 10 ft = 125 sq ft.

To measure a whole floor, repeat this for every room and add the results. The calculator does the adding for you: tap Add another room, give each one a name, and the total updates as you type. The room schedule next to the result lists every room, which is what you hand to a flooring store or contractor.

Area formulas for other shapes

Shape	Formula	Example	Area
Rectangle or square	length × width	14 × 12 ft	168 sq ft
L-shaped room	(L₁ × W₁) + (L₂ × W₂)	20 × 12 + 8 × 6 ft	288 sq ft
Circle	π × (diameter ÷ 2)²	10 ft across	78.54 sq ft
Triangle	base × height ÷ 2	10 ft base, 8 ft high	40 sq ft
Trapezoid	(side a + side b) ÷ 2 × height	10 and 14 ft sides, 8 ft apart	96 sq ft

The height of a triangle or trapezoid is measured at a right angle to the base, not along a slanted wall.

Rooms that are not rectangles

Very few rooms are perfect rectangles. The method is always the same: break the floor into simple shapes, find each area, then add or subtract.

L-shaped and T-shaped rooms — two or three rectangles that do not overlap. Choose L-shape or add each part as a separate room.
Bay windows — a trapezoid on top of the main rectangle.
Rounded alcoves — half a circle: π × radius² ÷ 2. A 6 ft-wide alcove is 3.14 × 3² ÷ 2 = 14.1 sq ft; add it as a Known area.
Things you will not cover — a kitchen island, a fireplace hearth, a built-in tub or a stairwell opening. Tap Subtract a cut-out: the piece is drawn in ochre and its area comes off the total.

Closets are usually included when you buy flooring for a bedroom, because the floor runs into them. Add a closet as its own small room so you can see it on the schedule.

Square footage of a whole house: what counts

The number in a home listing is not the same as the sum of your room measurements. Since 2022, Fannie Mae has required appraisers to measure homes using ANSI Z765-2021, the American National Standard for single-family square footage. The main rules:

Exterior dimensions. The house is measured around the outside walls, so wall thickness is included. That is why listed square footage is larger than the floor you would carpet.
Finished area only. The space must be suitable for year-round use, with walls, floors and ceilings finished like the rest of the house, and reachable directly from other finished space.
Ceiling height of at least 7 ft. Under a sloped ceiling, at least half of the room must have 7 ft of headroom, and no part with less than 5 ft counts.
Above and below grade are separate. A finished basement is reported on its own line, not added to the above-grade total.
Not included: garages, unfinished basements and attics, open porches and decks, and openings in an upper floor such as a two-story foyer.

If you are checking a listing or an appraisal, measure the outside of the house. If you are buying materials, measure inside each room — that is what this calculator is set up for.

How much extra to buy for waste

You will always cut some pieces to fit walls, doorways and corners, and some boards or tiles arrive damaged. Order more than the measured area:

How it is installed	Extra to add	Why
Planks or tile laid straight	5 %	Cuts only at the walls
Tile, vinyl, most patterns	10 %	More cuts; spares from the same dye lot
Diagonal, herringbone, many angles	15 %	Every edge piece is cut at an angle

Mullican Flooring recommends adding 5–7 % for hardwood laid straight and 10–15 % on a diagonal; Daltile recommends buying about 10 % more tile than you measured. Lower-grade boards with more knots and color variation may need extra on top, because the installer sets aside pieces you do not want on the floor.

Choose the matching preset under Extra for waste, or type your own percentage.

How many boxes of flooring you need

Flooring is sold by the box, and every box lists how many square feet it covers — often between 18 and 30 sq ft for laminate and vinyl plank. To find the number of boxes:

boxes = (square footage × (1 + waste %)) ÷ coverage per box, rounded up

For a 14 × 12 ft room with 10 % waste and boxes of 22.69 sq ft: 168 × 1.10 = 184.8 sq ft, and 184.8 ÷ 22.69 = 8.14, so you buy 9 boxes. Always round up — stores will not sell a fraction of a box. Open Boxes and price in the calculator, type the coverage from the box label, and the count appears with the result.

Keep one unopened box after the job. If a board is damaged years later, a match from the same production run is hard to find.

Common room sizes in square feet

Room size	Square feet	Square meters	With 10 % waste
8 × 10 ft	80	7.43	88
10 × 10 ft	100	9.29	110
10 × 12 ft	120	11.15	132
12 × 12 ft	144	13.38	158
12 × 14 ft	168	15.61	185
12 × 16 ft	192	17.84	211
14 × 16 ft	224	20.81	246
16 × 20 ft	320	29.73	352
20 × 24 ft	480	44.59	528

A typical U.S. secondary bedroom is 10 × 10 to 10 × 12 ft, a primary bedroom 12 × 14 to 14 × 16 ft, and a two-car garage about 20 × 24 ft.

Converting square feet to yards, meters and acres

From	To	Multiply by	Exact?
square feet	square meters	0.09290304	yes — 1 ft = 0.3048 m exactly
square meters	square feet	10.7639104	rounded
square feet	square yards	÷ 9	yes — 1 yd = 3 ft
square feet	acres	÷ 43,560	yes
acres	square feet	43,560	yes

Carpet is often priced per square yard: divide square feet by 9 and compare. A 168 sq ft room is 18.67 sq yd. The calculator shows the result in square feet, square meters, square yards and acres at the same time, and you can enter a price per square foot or per square yard.

What to calculate next

Square footage is the first step for most projects. For a slab or a footing, take the area to the concrete calculator; for a driveway or a path, the gravel calculator turns square feet and depth into cubic yards and tons. For loose material in beds, use the mulch calculator or the topsoil calculator, and for any other volume the cubic yards calculator.