Square footage calculator
Pick the shape, enter the measurements in the unit you have, and read the area in square feet, square metres and square yards. Add a price per square foot to get the cost of material, waste included.
Square footage calculator
11.15 square metres, 13.33 square yards.
Formulas: rectangle = length x width; triangle = base x height / 2; circle = 3.1416 x (diameter / 2)^2; L-shape = the two rectangles added. 1 square metre = 10.764 square feet.
How to measure a room
Measure along the floor at the base of the walls, from drywall to drywall, and write each measurement in feet with the inches as a decimal: 3 inches is 0.25 feet, 6 inches is 0.5, 9 inches is 0.75. Measure both long walls and both short walls; old houses are rarely square, and the larger of each pair is the safe figure for material. Doorways count as part of the floor you cover. A closet is its own small rectangle, added to the room.
For a whole floor of a house, measure room by room and add, rather than the outside of the building: exterior walls, interior walls and stairwells can take up 10 percent or more of the footprint, and you do not buy flooring for them.
Odd shapes: split them and add
Any floor plan breaks into shapes the calculator knows. An L-shaped room is two rectangles. A room with a bay window is a rectangle plus a half circle or a trapezoid (average the two parallel sides, multiply by the depth). A gable end for siding is a rectangle plus a triangle. Sketch the room, draw the cutting lines, number the pieces, measure each, and run them one at a time. Write the pieces down: the list is what you hand to the installer for a quote, and what you check the quote against.
Square feet, square metres and square yards
Flooring in the United States is priced by the square foot, carpet often by the square yard, and most of the world works in square metres. The conversions are fixed:
| From | To | Multiply by |
|---|---|---|
| square feet | square metres | 0.0929 |
| square metres | square feet | 10.764 |
| square feet | square yards | 0.1111 (divide by 9) |
| square yards | square feet | 9 |
| acres | square feet | 43,560 |
Exact definitions: 1 foot = 0.3048 metre, so 1 square foot = 0.09290304 square metre (NIST).
What counts in a house's square footage
The number on a real estate listing is not the sum of the rooms. For a mortgage appraisal, Fannie Mae's Selling Guide requires appraisers to measure and report gross living area under the ANSI Z765 standard, which measures finished, above-grade living space from the outside of the exterior walls, floor by floor, and excludes garages, below-grade space such as basements, unfinished attics, and open porches. Two houses with the same rooms can list 10 percent apart depending on whether a finished basement or a bonus room above the garage was counted. If you are comparing listings or checking a tax assessment, ask which standard was used.
Buying material: area plus an allowance
Flooring, tile and carpet are cut to fit, and the offcuts at the walls, around fixtures and at the ends of planks do not go back in the box. Installers add an allowance on top of the measured area, larger for diagonal and patterned layouts and for rooms with many corners, and round up to whole boxes. The calculator applies the percentage you enter and gives the cost at your price per square foot; buy whole boxes and keep one unopened for repairs, since dye lots change.
Questions people ask
How do I calculate the square footage of a room?
Measure the length and the width in feet, including inches as a decimal (6 inches is 0.5 feet), and multiply them. A room 12 feet by 10 feet 6 inches is 12 x 10.5, or 126 square feet. Measure at floor level along the walls, and ignore baseboards.
How do I measure a room that is not a rectangle?
Split it into rectangles, triangles and half circles, measure each, and add them. An L-shaped room is two rectangles; a bay window is a rectangle plus a trapezoid or half circle. The calculator has an L-shape option for the most common case.
How many square feet are in a square metre?
One square metre is 10.764 square feet, and one square foot is 0.0929 square metres. To convert square feet to square metres, divide by 10.764; the calculator does it for you.
Does square footage include closets and hallways?
For flooring, yes: anything you will cover counts, closets included. For the square footage of a house in a listing, appraisers in the United States generally follow the ANSI Z765 standard, which counts finished, heated space measured from the exterior walls and leaves out garages, unfinished basements and open porches.
How much extra flooring should I buy?
Installers add an allowance for cuts, breakage and matching patterns, and more for diagonal layouts, herringbone and rooms with many corners. Enter the allowance you want in the calculator; the material cost line applies it to the area.
Sources
- Fannie Mae Selling Guide, B4-1.3-05 Improvements section of the appraisal report: appraisers must measure and report gross living area under ANSI Z765 (finished, above-grade space, exclusions), read 25 October 2026.
- National Institute of Standards and Technology, Guide for the use of the SI (SP 811), Appendix B.9 conversion factors: 1 square foot = 0.09290304 square metre, read 25 October 2026.