How to work out square footage
Square footage is length multiplied by width, both in feet. A room 12 feet
6 inches by 10 feet 3 inches is 12.5 × 10.25 = 128.125 square feet. The part
that costs people money is the inches: 12 feet 6 inches is 12.5 feet, not 12.6
feet. Type it as 12' 6" and the box above does the conversion and
shows you what it read.
For a room that is not a rectangle, add a second area instead of averaging. An L-shaped room is two rectangles. A room with an island or a stair opening is one rectangle with a second one subtracted. Each area you add gets its own row in the breakdown with its share of the total, which is the fastest way to catch a measurement typed into the wrong box.
Measuring a room you can actually walk into
Measure at the floor, not at waist height, and measure to the face of the baseboard rather than the wall behind it if you are buying flooring. Take each wall twice. Old houses are rarely square: if the two ends of a room differ by more than an inch, use the larger figure for ordering and the smaller one for anything that has to fit.
For an odd shape, break it into rectangles on paper first and measure each one. Three rough rectangles beat one careful guess at an average. For a curved bay, treat it as a half circle and use the circle shape with the diameter across the opening.
Square feet, square yards, square meters, acres
All four appear above at once because different trades quote in different units. Carpet and some flooring is priced by the square yard: one square yard is nine square feet. Square meters use the exact factor, 1 ft² = 0.09290304 m², which comes from the inch being defined as 25.4 millimeters. Land is in acres, at 43,560 square feet to the acre.
A square foot and a linear foot are not the same thing and are not interchangeable. Baseboard, trim and fencing are bought by the linear foot, so the perimeter is shown as well as the area.
Waste
This page starts at zero waste, because what you measured is what you measured. Waste belongs to the material, not to the room: tile laid on a diagonal wastes more than tile laid square, and a patterned carpet wastes more than a plain one. Five to ten per cent is the usual starting point for a simple rectangular room. Set it here if you want the figure carried forward, and set it only once — adding ten per cent twice is a mistake we found on more than one large retailer's calculator.
Reporting a home's living area
If the number is going into a listing or an appraisal, it has to follow a measuring standard rather than a tape alone. The usual one for single-family homes in the United States is ANSI Z765. In short: finished floor area counts only where the ceiling is at least 7 feet high; under a sloped ceiling nothing below 5 feet counts and at least half the room has to reach the full height; floor area below grade is reported separately from the area above it; and the reported figure is rounded to whole square feet.
Tick the ANSI box above and the page reports that way and tells you which of those conditions it cannot check for you. It will not claim a condition is met on your say-so unless you say so: that is why two of the three checks start as "not checked" rather than as a pass.
Common questions
How do I type feet and inches?
Any of these work in one box: 12' 6", 12ft 6in,
12-6, 12 6. Fractions work too: 12' 6 1/2"
or 12 6 1/2. Metric works: 3.2m, 320cm,
3200mm. Whatever you type, the line under the box says what it was
read as before you trust it.
Why does the page show a number before I type anything?
Because an empty calculator is no use. The page opens on a common case — a room 12 feet 6 inches by 10 feet 3 inches — so you can see the shape of the answer and change the numbers to yours.
Can I send someone this calculation?
Yes. Copy link puts the whole project in the address, areas and all, and the link opens with exactly these measurements. Nothing is stored on our side and nothing is needed from you — no email, no postcode, no account.
How many square feet is a 12x12 room?
144 square feet, which is 16 square yards and 13.38 square meters. A 10x10 room is 100 square feet; a 12x16 room is 192.