A square footage calculator turns two measurements into the figure used as the basis for flooring or painting quotes, as well as for rental listings. Simply measure the length and width of a room; the area is calculated by multiplying these two values.
Enter your measurements below. You can add as many areas as you like, switch units (feet, inches, yards, or meters), and simultaneously view the total in square meters, square yards, and acres.
How the Square Footage Calculator Works
For any rectangular room, the area is calculated by multiplying the length by the width. A room measuring 12 by 10 feet has an area of 120 square feet. This simple calculation allows you to measure the vast majority of rooms in most homes.
The calculator above performs two functions that would normally require manual calculations: it adds up multiple areas—allowing you to determine the total area of a floor or an entire house in a single step—and it converts the result into other units as you enter the data; this means you do not need to use another tool to find out the equivalent in square meters of your 420 square feet.
How to Measure the Square Footage of a Room
It takes just three steps, and the only tool needed is a tape measure.
- Measure the length of the room at its longest point, from wall to wall.
- Measure the width in the same way, at its widest point.
- Multiply the two figures together or enter them above.
Measure to the wall itself, not the baseboard; keep the tape measure flat against the floor rather than angled, as a sagging tape can imperceptibly add extra inches. If a measurement falls between two markings, use decimals instead of fractions. “Ten feet and six inches” equals 10.5 feet—a figure much easier to multiply than “ten feet and half a foot.”
Measuring L-shaped or irregularly shaped rooms
Few homes consist solely of simple rectangles, and that is precisely where most people encounter difficulties. The trick is not to view the room as a single, continuous shape.
Divide the room into rectangles. An L-shaped living room is made up of two rectangles. A room with a bay window can be broken down into a rectangle and the area of the bay window itself. A hallway that turns at a right angle consists of two rectangles joined at the bend. Measure each section separately, enter the corresponding values as distinct areas, and the calculator will add them up automatically.
For a triangular area, measure the base and the height, multiply them together, and divide the result by two. For a circular area, measure the distance across the center to get the diameter; divide this value by two to determine the radius, then multiply the radius by itself and by 3.14.
Converting square feet to other units
The calculator performs the conversion as you enter the data; however, reference values are provided here should you wish to verify the calculation or perform it manually. All of these are fixed definitions maintained by the NIST Office of Weights and Measures:
- 1 square meter = 10.764 square feet (therefore, divide the value in square feet by 10.764 to obtain square meters)
- 1 square yard = 9 square feet (therefore, divide the value by 9)
- 1 acre = 43,560 square feet (therefore, divide the value by 43,560)
- 1 square foot = 144 square inches
Converting to acres often yields surprising results. An acre equals 43,560 square feet; this means that a typical quarter-acre residential lot measures approximately 10,890 square feet, and a 2,000-square-foot house built on it occupies less than one-fifth of the land area.
Square feet, cubic feet, and cubic yards
Square footage measures a flat surface. The moment depth enters the picture, you need cubic measurements instead, and this is where a lot of ordering mistakes happen.
Flooring, paint, tiles, and turf are bought by area, so square feet is the right unit. Anything poured or spread to a depth is bought by volume: concrete, topsoil, mulch, gravel, and sand are all sold by the cubic yard.
To get from one to the other, multiply your square footage by the depth in feet, which gives cubic feet, then divide by 27 to get cubic yards. A 400 square foot patio poured 4 inches deep is 400 multiplied by 0.333, giving roughly 133 cubic feet, which is about 4.9 cubic yards of concrete. Suppliers generally sell in quarter or half yard increments, so that order rounds up to 5 cubic yards.
How much extra material should you order?
The square footage of your room is not the same as the amount of material you need to buy. Any flooring or tile installation results in offcuts, as planks and tiles rarely fit the room’s dimensions perfectly.
- Simple, linear installation patterns: allow for approximately 5% extra for offcuts.
- Rooms with angles, alcoves, or multiple doorways: allow for approximately 10%.
- Diagonal or herringbone installation: allow for 15% or more, as each cut creates a wedge-shaped scrap that cannot be reused.
For example, for a 420-square-foot room (approx. 39 m²) with a straight installation pattern, you should order about 440 square feet (approx. 41 m²) of flooring. It is also recommended to keep the offcuts from the same batch, as products ordered later often show slight variations in shade.
What square footage is used for
Flooring, paint, and tiling quotes are all priced per square foot or per square metre, which is why the calculator above includes an optional price field. Enter what you are being charged per square foot and it works out the total.
Beyond materials, square footage is how homes are listed and compared, how commercial rent is charged, and how heating and cooling capacity is specified. If you are working out what a property costs to own rather than to floor, our mortgage calculator and property tax calculator both work from the purchase price. In most countries, published floor area excludes garages, unfinished basements, and lofts, so a listed figure and the figure you measure yourself will not always agree.
Square footage is the starting point for most material estimates. See all our construction calculators for concrete, gravel, and asphalt.
How do you calculate square footage?
Multiply the room’s length by its width, expressing both measurements in feet. A room that is 12 feet long and 10 feet wide has an area of 120 square feet.
How do you calculate the square footage of an L-shaped room?
Divide it into two rectangles, measure them separately, and add the two areas together. Using the calculator above, you can enter each rectangle as a separate area.
How many square feet are in an acre?
43,560 square feet. To convert square feet to acres, divide the value by 43,560.
How do you convert square feet to square meters?
Divide the value by 10.764. Thus, 1,000 square feet is equivalent to approximately 92.9 square meters.
Should I measure to the wall or to the baseboard?
Measure to the wall. If you measure to the baseboard, the room’s area will be underestimated, which could lead to a shortage of material during installation.
How much extra flooring should I buy?
Allow for approximately 5% extra for a simple straight installation, 10% for rooms with angles or alcoves, and 15% or more for diagonal or herringbone installations.