Square Footage Calculator

List each room or section as length x width to get the total area in square feet, square yards and square metres, with waste and cost added.

Runs in your browserFree, no sign-upLast reviewed October 13, 2026

Square footage

Total area: 323 sq ft; 3 areas
Square yards: 35.89 sq yd; sq ft ÷ 9
Square metres: 30.01 m²; sq ft x 0.09290304
Square inches: 46,512 sq in; sq ft x 144
With 10% waste: 355.3 sq ft; 39.48 sq yd, 33.01 m²
Estimated cost: 1,598.85; 355.3 sq ft x 4.50, waste included
Cost without waste: 1,453.50; 323 sq ft x 4.50

Area by line

#	Name	Dimensions	Formula (feet)	Area (sq ft)
1	Living room	15' 6" x 12'	15.5 x 12	186
2	Kitchen	10' x 9' 6"	10 x 9.5	95
3	Hallway	12' x 3' 6"	12 x 3.5	42
	Total			323

Summary

Total area: 323 sq ft (35.89 sq yd, 30.01 m²). With 10% waste: 355.3 sq ft. Estimated cost at 4.50 per sq ft: 1,598.85.

About the figures. Areas are calculated from the full measurements and rounded to two decimal places for display. The cost uses the area including the waste allowance, because that is the amount of material you buy.

Quick answers

How do you calculate square footage?: Multiply the length in feet by the width in feet. A room 12 feet long and 10 feet wide is 12 x 10 = 120 square feet. For an L-shaped or irregular room, split it into rectangles, work out each one and add them together.
How do you calculate square feet from feet and inches?: Convert the inches to a decimal of a foot by dividing by 12, then multiply. A room 12 ft 6 in by 10 ft 3 in is 12.5 x 10.25 = 128.13 square feet. Multiplying the feet and the inches separately gives the wrong answer.
How many square feet is a 12x12 room?: 144 square feet, which is 16 square yards or 13.38 square metres. With a 10% waste allowance for flooring you would buy 158.4 square feet.
How do I find the square footage of a circle?: Multiply pi by the radius squared, where the radius is half the distance across. A circle 10 feet across has a radius of 5 feet, so its area is 3.14159 x 5 x 5 = 78.54 square feet.
How do I find the square footage of a triangle?: Multiply the base by the height and halve the result. The height is measured straight up from the base to the opposite corner, not along a sloping side. A triangle with a 12 foot base and an 8 foot height is 48 square feet.
How do you convert square feet to square yards?: Divide by 9, because a square yard is 3 feet by 3 feet. 180 square feet is 20 square yards. Carpet is often priced by the square yard, so this is the figure to compare with a carpet quote.

Why use Square Footage Calculator

Square footage is length multiplied by width, with both measured in feet. This square footage calculator does that for as many areas as you list, one per line, and adds them up. Measurements can be typed as plain feet (12 x 10), feet and inches (12' 6" x 10' 3"), or with a unit such as 150 in or 3.5 m. Lines that start with circle or triangle use those formulas instead, and a line that starts with a minus sign is subtracted. The result gives the total in square feet, square yards, square metres and square inches, the area with a waste allowance, and an estimated cost from a price per square foot.

Square footage of common room sizes

Each row is the calculator's result for a rectangle of that size in feet, with a 10% waste allowance.

Room size (ft)	Square feet	Square yards	Square metres	With 10% waste
8 x 10	80	8.89	7.43	88 sq ft
10 x 10	100	11.11	9.29	110 sq ft
10 x 12	120	13.33	11.15	132 sq ft
11 x 12	132	14.67	12.26	145.2 sq ft
12 x 12	144	16	13.38	158.4 sq ft
12 x 14	168	18.67	15.61	184.8 sq ft
12 x 15	180	20	16.72	198 sq ft
13 x 15	195	21.67	18.12	214.5 sq ft
14 x 16	224	24.89	20.81	246.4 sq ft
15 x 20	300	33.33	27.87	330 sq ft
16 x 20	320	35.56	29.73	352 sq ft
20 x 20	400	44.44	37.16	440 sq ft
20 x 24	480	53.33	44.59	528 sq ft
24 x 24	576	64	53.51	633.6 sq ft
30 x 40	1,200	133.33	111.48	1,320 sq ft

Square footage formulas by shape

Rectangle: length x width. Circle: pi x radius x radius (radius = diameter / 2). Triangle: base x height / 2. All measurements in feet.

Convert every measurement to feet before multiplying: inches divided by 12, yards multiplied by 3, metres divided by 0.3048. The calculator does this for you and shows the converted numbers in the Formula (feet) column, so 15' 6" x 12' appears as 15.5 x 12 = 186. To change the total into other units, divide square feet by 9 for square yards, multiply by 0.09290304 for square metres, or multiply by 144 for square inches. Totals of 4,356 square feet or more also show acres, at 43,560 square feet to the acre.

Worked examples

Real results from the calculator, with the inputs that produced them.

Three rooms of flooring with waste and cost

Areas: Living room: 15' 6" x 12' / Kitchen: 10 x 9.5 / Hallway: 12 x 3' 6". Waste allowance 10%. Cost per sq ft 4.50

186 + 95 + 42 = 323 sq ft (35.89 sq yd, 30.01 m2). With 10% waste: 355.3 sq ft. Estimated cost 1,598.85; cost without waste 1,453.50.

An L-shaped room split into two rectangles

Areas: Main: 18 x 14 / Alcove: 6 x 4. Waste allowance 10%. Cost per sq ft 3.50

252 + 24 = 276 sq ft. With 10% waste: 303.6 sq ft. Estimated cost 1,062.60.

Subtracting a hearth that will not be floored

Areas: Room: 14 x 13 / -Hearth: 5 x 2. Waste allowance 10%

182 - 10 = 172 sq ft (19.11 sq yd). With 10% waste: 189.2 sq ft.

Feet and inches with a fraction

Areas: Bedroom: 12' 3 1/2" x 10' 9". Waste allowance 0%

132.14 sq ft (14.68 sq yd, 12.28 m2).

A deck, a round patio and a gable end together

Areas: Deck: 16 x 12 / Patio: circle 10 / Gable: triangle 24 x 8. Waste allowance 15%. Cost per sq ft 6

192 + 78.54 + 96 = 366.54 sq ft. With 15% waste: 421.52 sq ft. Estimated cost 2,529.12.

A room measured in metres

Areas: 4.2 x 3.6. Unit for plain numbers Metres. Waste allowance 8%

162.75 sq ft, which is 15.12 m2. With 8% waste: 175.77 sq ft.

Square footage of a circle by diameter

For round patios, rugs, pools and tables. Enter these as circle followed by the diameter.

Diameter (ft)	Square feet	Square yards	Square metres
6	28.27	3.14	2.63
8	50.27	5.59	4.67
10	78.54	8.73	7.3
12	113.1	12.57	10.51
15	176.71	19.63	16.42
18	254.47	28.27	23.64
24	452.39	50.27	42.03

Doubling the diameter multiplies the area by four: an 8 foot circle is 50.27 sq ft and a 24 foot circle, three times as wide, is nine times that.

Measurement formats the calculator accepts

Plain numbers, read in the unit you choose: 12 x 10 or 12.5 x 10.25.
Feet and inches with marks: 12' 6" x 10' 3". A bare number after a feet mark is read as inches, so 12' 6 also works.
Feet and inches with words: 12 ft 6 in x 10 ft, or 12 feet 6 inches by 10 feet.
Fractions of an inch: 12' 6 1/2" x 10'.
A unit on a single measurement, whatever the default unit is: 150 in x 96 in, 4 yd x 5 yd, 3.5 m x 400 cm.
The separator can be x, a multiplication sign, an asterisk or the word by.
Shapes: circle 8 (diameter), circle radius 4, triangle 10 x 6 (base x height).
Subtraction: start the line with a minus sign, as in -4 x 2.5, to take an area off the total.

Waste allowance, cost and what the total does not include

Flooring, tile, turf and sheet materials are cut to fit, and the offcuts are often unusable, so you buy more than the measured area. The Waste allowance adds a percentage on top of the total: 323 square feet with 10% waste is 355.3 square feet. A figure of around 10% is a common starting point for straight-laid flooring, with more for diagonal or patterned layouts and rooms with many corners, but the right number depends on the product, so follow the manufacturer's or installer's guidance.

The estimated cost multiplies the price per square foot by the area including waste, because that is the quantity you pay for. The cost without waste is shown next to it for comparison. No currency symbol is added, so the figure is in whatever currency you typed the price in. Materials sold by the box or roll have to be rounded up to whole units, which the calculator does not do.

The result is floor or surface area only. It does not work out wall area for paint, which needs the room height and openings; the paint calculator handles that. To convert a finished area into acres, hectares or other units, use the area converter. Up to 50 lines can be entered at once.

How to get your result

1
In Areas, one per line, type each rectangle as length x width, for example 12 x 10 or 15' 6" x 12'. Put a name before a colon if you want one: Kitchen: 10 x 9.5.
2
For other shapes, start the line with the shape: circle 8 for a circle 8 feet across, circle radius 4, or triangle 10 x 6 for base x height.
3
Set Unit for plain numbers if your bare numbers are inches, yards, metres or centimetres rather than feet.
4
Enter a Waste allowance (%) for material you will lose to cuts, or 0 for the plain area.
5
Enter a Cost per sq ft (optional) to get an estimated cost, or clear the box to skip it.
6
Read the Total area and its conversions, then check the Area by line table for each section.

Questions people ask

How do I measure an L-shaped room?

Split it into two rectangles that do not overlap, measure each one and enter them on separate lines. An 18 x 14 main area with a 6 x 4 alcove is 252 + 24 = 276 square feet. The same approach works for any room made of right-angled sections.

Is square footage the same as square feet?

Yes. Square footage is the size of an area measured in square feet. A square foot is a square one foot on each side, so 120 square feet means 120 of those squares would cover the floor.

Why is 12 ft 6 in by 10 ft 3 in not 120.18 square feet?

Because feet and inches cannot be multiplied separately and joined with a decimal point. Six inches is half a foot (0.5), and three inches is a quarter (0.25), so the sum is 12.5 x 10.25 = 128.13 square feet.

Can I enter measurements in inches or metres?

Yes. Either add the unit to the number, as in 150 in x 96 in or 3.5 m x 4 m, or change Unit for plain numbers so every bare number is read in inches, yards, metres or centimetres. The answer is still given in square feet first.

How many square feet are in a square metre?

About 10.764. One square foot is exactly 0.09290304 square metres, so a room of 100 square feet is 9.29 square metres and a 4.2 m by 3.6 m room (15.12 square metres) is 162.75 square feet.

Does the calculator handle circles measured by radius?

Yes. A line such as circle 8 treats the number as the diameter. Write circle radius 4 to give the radius instead; both describe the same circle and return 50.27 square feet.

How do I leave out an area that will not be covered?

Add it on its own line with a minus sign in front. A 14 x 13 room with a 5 x 2 hearth entered as -5 x 2 comes to 172 square feet instead of 182. The total must stay above zero.

How much does it cost to floor a room per square foot?

Multiply the area you need to buy, including waste, by the price per square foot. At 4.50 per square foot, 355.3 square feet costs 1,598.85. Underlay, trims, delivery and fitting are extra and are not part of the estimate.