How to Calculate Square Footage of a Room (With Examples)

Short answer: measure the room’s length and width in feet and multiply them. A room 12 ft by 10 ft is 12 × 10 = 120 square feet. If the room isn’t a plain rectangle, split it into rectangles (and the odd triangle or circle), work out each piece, and add them up.

To skip the math, enter your measurements in the square footage calculator. It handles rectangles, L-shapes, triangles and circles, and converts to square yards and square meters.

Step by step

1. Measure the length of the room wall to wall, at floor level, with a tape measure.
2. Measure the width the same way, at right angles to the length.
3. Turn inches into decimal feet (table below). 14 ft 6 in becomes 14.5 ft.
4. Multiply length × width. That’s the floor area in square feet.

Example: a bedroom 14 ft 6 in by 11 ft 3 in is 14.5 × 11.25 = 163.13 sq ft (18.13 sq yd, or 15.15 m²).

Inches to decimal feet

Inches	Feet	Inches	Feet
1 in	0.08	7 in	0.58
2 in	0.17	8 in	0.67
3 in	0.25	9 in	0.75
4 in	0.33	10 in	0.83
5 in	0.42	11 in	0.92
6 in	0.5	12 in	1

Divide the inches by 12. Don’t write 14 ft 6 in as 14.6: that’s off by a tenth of a foot on every side you measure.

Rooms that aren’t rectangles

L-shaped rooms

Split the L into two rectangles, without overlapping, and add them. A 20 × 12 ft space plus a 10 × 8 ft leg is 240 + 80 = 320 sq ft.

Closets and alcoves

Treat them as extra rectangles. A 12 × 11 ft bedroom with a 6 × 2 ft closet is 132 + 12 = 144 sq ft of floor.

Bay windows and angled corners

A triangle is base × height ÷ 2. A bay that sticks out 3 ft across a 6 ft opening adds 6 × 3 ÷ 2 = 9 sq ft. A bay with flat sides is a rectangle plus two small triangles.

Round areas

A circle is 3.1416 × radius × radius (the radius is half the diameter). A round area 10 ft across is 3.1416 × 5 × 5 = 78.54 sq ft.

Common room sizes

Room	Square feet	Square meters
10 × 10 ft	100	9.29
10 × 12 ft	120	11.15
12 × 12 ft	144	13.38
12 × 14 ft	168	15.61
14 × 16 ft	224	20.81
15 × 20 ft	300	27.87
20 × 20 ft	400	37.16

Square footage of several rooms or a whole floor

Work out each room on its own, then add the totals. Write each one down with its sketch so you can check it later. Hallways and closets count if you’re buying flooring for them.

The total will usually be smaller than a home’s listed square footage. Listings measure the house differently (walls and stairs are often included, and the rules vary), so room-by-room totals are the right number for buying materials, not for comparing with a listing.

Buying flooring or paint? Add extra

Cuts and mistakes waste material, so order more than the bare area. For the 163.13 sq ft bedroom, 10% extra is 179.4 sq ft. The flooring calculator turns that into boxes, and the tile and paint calculators work from wall and floor sizes too.

Common questions

How do I convert square feet to square meters?

Multiply by 0.0929 (exactly 0.09290304). 120 sq ft is 11.15 m².

How do I convert square feet to square yards?

Divide by 9, because a square yard is 3 ft × 3 ft. 120 sq ft is 13.33 sq yd.

Do I measure to the baseboard or the wall?

Measure wall to wall at floor level. For flooring, the small strip under the baseboard is covered by your extra allowance.

How many square feet is a 12 × 12 room?

144 square feet.

Sources

• NIST Handbook 44: unit conversions (1 sq ft = 0.09290304 m²; 1 sq yd = 9 sq ft).