Square Footage Calculator for Rooms of Any Shape

Estimate only. Check product labels and local building rules before you buy or build.

Quick answer

Square footage is length × width in feet for a rectangular room. For any other floor, split it into rectangles, triangles, circles or trapezoids, work out each part and add them up: a 12 × 15 ft room (180 sq ft) plus a 10 × 12 ft room (120 sq ft) is 300 sq ft. Multiply square feet by 0.09290304 to get square meters, so 300 sq ft is 27.87 m².

How to use the square footage calculator

Choose how you measured: feet, feet and inches, inches or yards. Switch to metric for meters, centimeters or millimeters. Numbers you have already typed are converted.
For each room or part of a room, pick its shape and type the measurements. The drawing shows the shape you entered, and the area appears next to it.
Add an area for every room or section of floor. Set an area to Subtract for anything inside a room that you will not cover, such as a kitchen island or a fireplace hearth.
Read the total in square feet, with square meters and square yards below it. An area with a missing measurement is left out of the total until you fill it in.

How do you calculate square footage?

Multiply the length by the width, both in feet: a room 12 ft long and 15 ft wide is 12 × 15 = 180 sq ft. For a floor that is not a rectangle, split it into simple shapes, work out each one with the formulas below and add the results. Subtract anything you will not cover.

If you measured in inches, divide the result by 144 to get square feet, because a square foot is 12 × 12 inches. A square yard is 3 × 3 ft, so divide square feet by 9 to get square yards. One foot is exactly 0.3048 m, so one square foot is exactly 0.09290304 m².

rectangle = length × widthL-shape = overall length × overall width − missing corner length × missing corner widthtriangle = base × height ÷ 2triangle from sides a, b, c: s = (a + b + c) ÷ 2, area = √(s × (s − a) × (s − b) × (s − c))circle = π × (diameter ÷ 2)²trapezoid = (parallel side 1 + parallel side 2) ÷ 2 × distance between themsquare meters = square feet × 0.09290304square yards = square feet ÷ 9

Square footage of common room sizes

Each value is length × width, converted with 1 sq ft = 0.09290304 m² and 1 sq yd = 9 sq ft, and rounded to two decimals.

Common room sizes in square feet, square meters and square yards
Room size	Square feet	Square meters	Square yards
10 × 10 ft	100	9.29	11.11
10 × 12 ft	120	11.15	13.33
12 × 12 ft	144	13.38	16.00
12 × 14 ft	168	15.61	18.67
12 × 16 ft	192	17.84	21.33
14 × 16 ft	224	20.81	24.89
15 × 20 ft	300	27.87	33.33
20 × 20 ft	400	37.16	44.44
20 × 24 ft	480	44.59	53.33
24 × 30 ft	720	66.89	80.00

Worked examples

An L-shaped living room

The room is 24 ft along its longest wall and 18 ft across, with a 10 ft × 8 ft corner taken up by the entry hall. Choose L-shape and enter 24, 18, 10 and 8.

The full rectangle is 24 × 18 = 432 sq ft and the missing corner is 10 × 8 = 80 sq ft, so the room is 432 − 80 = 352 sq ft. That is 32.7 m², or 39.11 sq yd.

A kitchen in feet and inches, with a bay window and an island

Set Measure in to Feet and inches. The kitchen is 13 ft 6 in by 12 ft, which is 13.5 × 12 = 162 sq ft. The bay window is a trapezoid 8 ft along the wall, 4 ft across the front and 2 ft deep: (8 + 4) ÷ 2 × 2 = 12 sq ft.

The 6 ft × 3 ft island will not get new flooring, so add it as a third area set to Subtract: 18 sq ft. The total is 162 + 12 − 18 = 156 sq ft, or 14.49 m².

What counts toward a home’s square footage?

An appraisal for a loan sold to Fannie Mae reports above-grade and below-grade square footage separately. Fannie Mae’s Selling Guide requires appraisers to measure single-family homes with the ANSI Z765-2021 standard, and it treats a level as below grade if any part of it is below grade, however well it is finished. A finished walk-out level that is partly below grade is therefore left out of the above-grade figure.

Finished rooms that do not meet the standard’s ceiling height requirements, or that you reach only through unfinished space, are also reported on their own line, and everything that is not finished area under the standard is reported as unfinished. For a flooring or paint job none of this applies: measure every surface you will cover.

How do I measure a room that is not a rectangle?

Split it into rectangles first, then use a triangle, trapezoid or circle only for the parts that are left. Measure wall to wall at floor level and write each length down as you go. An L-shaped room is easiest as one big rectangle minus the missing corner, which is what the L-shape option does.

Where you cannot measure the height of a triangle at a right angle, measure its three sides and use the three-sides option. For a round room or a curved bay, measure the diameter straight across through the center. When you buy flooring or tile, add the cutting waste the product calls for on top of this area.

Questions

How many square feet is a 12×12 room?

A 12 × 12 ft room is 144 square feet. Multiply the length by the width in feet: 12 × 12 = 144. That is 13.38 m², or 16 square yards. If the room measures 12 ft 6 in each way, use 12.5 ft: 12.5 × 12.5 = 156.25 sq ft. Measure at floor level from wall to wall, and leave out closets unless you are covering them too.

How do I convert square feet to square meters?

Multiply square feet by 0.09290304 to get square meters, or divide by 10.764 for a close answer. The factor is exact because one foot is defined as exactly 0.3048 m, and 0.3048 × 0.3048 = 0.09290304. So 300 sq ft is 27.87 m², and 1,000 sq ft is 92.9 m². To go the other way, multiply square meters by 10.764.

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

Multiply the overall length by the overall width, then subtract the missing corner. A room 24 ft by 18 ft with a 10 ft by 8 ft corner cut out is 24 × 18 − 10 × 8 = 432 − 80 = 352 sq ft. You can also split the L into two rectangles and add them: 14 × 18 + 10 × 10 = 252 + 100 = 352 sq ft, the same answer.

How many square feet are in a square yard?

A square yard is 9 square feet, because a yard is 3 ft and 3 × 3 = 9. To turn square feet into square yards, divide by 9: a 12 × 15 ft room is 180 sq ft, which is 20 square yards. One square yard is 0.836 m². Check whether a price or a quote is per square foot or per square yard before you compare two of them.

Does a basement count in square footage?

Not in the above-grade square footage of an appraisal for a loan sold to Fannie Mae. Its Selling Guide requires appraisers to follow ANSI Z765-2021 and treats a level as below grade if any part of it is below grade, however well it is finished. A finished basement is reported on its own line and can still add value. For flooring, paint or heating, count it like any other room you will work on.

How do I calculate the square footage of a circle?

Multiply π by the radius squared, where the radius is half the diameter. A round room or patio 12 ft across has a radius of 6 ft, so its area is 3.1416 × 6 × 6 = 113.1 sq ft, or 10.51 m². For a half circle, such as a curved bay, work out the full circle and divide by 2. Measure the diameter through the center at its widest point.

Sources

National Institute of Standards and Technology (NIST), U.S. Survey Foot (checked October 19, 2026)One foot is exactly 0.3048 m; the U.S. survey foot was superseded by the international foot on January 1, 2023.
Fannie Mae, Selling Guide B4-1.3-05, Improvements Section of the Appraisal Report (checked October 19, 2026)Appraisers must use ANSI Z765-2021 for above- and below-grade square footage; any level partly below grade counts as below grade.

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Total floor area