Square footage is the standard way Americans measure floor space, from listing a home to buying the right amount of flooring. This calculator multiplies length by width to give you area in square feet, then scales it across multiple rooms and converts to other common units.
The basic formula
For any rectangular space, area equals length times width. A room that is 18 feet long and 14 feet wide covers 252 square feet. Measurements like 12 feet 6 inches go in as feet plus inches, and the calculator converts them to decimal feet (12.5 ft). If you are measuring several identical rooms, multiply that figure by the number of rooms. For L-shaped or irregular spaces, split the floor into rectangles, calculate each one separately, and add the areas together — the same trick contractors use on real job sites. Financing the project? The loan calculator estimates the monthly payment.
Estimating materials and cost
Once you know the area, buying materials becomes simple arithmetic. Multiply the total square footage by the price per square foot to estimate flooring, tile, or carpet costs. It is smart to add roughly 5 to 10 percent extra for cuts, waste, and future repairs, especially for patterned tile or hardwood that must be aligned; enter it as the waste allowance and the calculator shows the material to buy and prices the cost on it. Paint is figured differently — by wall area rather than floor area — so measure wall height and perimeter for those projects.
Converting between units
Square feet convert cleanly to other units when you need them. One square yard equals nine square feet, so divide by nine for carpet often sold by the yard. One square meter is about 10.76 square feet, useful when comparing international listings. Keeping the conversions handy means you can shop confidently no matter how a supplier prices their product. For acres, hectares and other units, use the area converter.
More worked examples
An L-shaped room: split the floor into two rectangles and run the calculator once for each. A 12 by 10 ft section is 120 ft² and an 8 by 6 ft section is 48 ft². With a 10% waste allowance and flooring at $3.25 per square foot, the first part needs 132 ft² of material costing $429.00, and the second needs 52.8 ft² costing $171.60. Add the two results for the whole room.
Measurements in feet and inches: three identical bedrooms measure 11 ft 6 in by 10 ft 9 in. Enter the feet and inches separately and set Number of rooms to 3. Each room is 123.63 ft², and the total is 370.88 ft², which the result also shows as 41.2 yd² and 34.46 m².
When to use this calculator
Use it to order flooring, carpet, tile, or underlayment; to estimate paint primer or sealant sold by coverage area; to compare a listing's square footage with a single room; or to price a job quoted per square foot. Leave the price blank when you only need the area, and set the waste allowance when you are buying material that has to be cut to fit.
Common mistakes
Typing inches into the feet field (for example 11.6 instead of 11 ft 6 in) understates the area; use the separate inches fields. Multiplying rooms of different sizes with Number of rooms only works for identical rooms, so measure different rooms separately. And for diagonal tile layouts or patterned carpet, ask your supplier what waste allowance they recommend before ordering.