Math
Square Footage Calculator
Enter a length and a width in feet, inches, yards or meters and get the area in square feet, along with square yards, square meters and acres, plus an estimated material cost at your price per square foot. Square footage drives most home-project math in the United States: flooring and tile are priced per square foot, carpet per square yard, paint by coverage, and real estate by the listing's finished area. The tool converts mixed units for you, so a room measured at 14 ft 6 in by 12 ft 3 in takes ten seconds instead of a pencil-and-paper conversion. Everything runs in your browser and nothing you enter leaves your device.
Your measurements
square feet
Assumes a rectangle; split irregular rooms into rectangles and add them. Costs exclude waste, tax and labor.
How the square footage calculator works
Area of a rectangle is length times width. The tool first converts both measurements to feet (inches divide by 12, yards multiply by 3, meters divide by 0.3048), multiplies them, and then converts the square-foot result to the other units. Because the foot is defined as exactly 0.3048 meters, every conversion here is exact and only the displayed decimals are rounded.
Formulas
square feet = length (ft) × width (ft) square yards = sq ft ÷ 9 · square meters = sq ft × 0.09290304 · acres = sq ft ÷ 43,5601 ft = 0.3048 m exactly, so 1 sq ft = 0.3048² = 0.09290304 sq m exactly
Notes & assumptions
- Both measurements use the same unit; pick it in the dropdown.
- For rooms with alcoves or an L shape, calculate each rectangle separately and add the areas.
- The cost row is materials only, before waste factor, tax and installation.
- Convert inches to decimal feet by dividing by 12 (6 in = 0.5 ft) if measuring in feet and inches.
Common room and area sizes
These reference figures cover the sizes that come up in real projects, from a small bedroom to a full lot. The square-meter column uses the exact factor 0.09290304.
| Dimensions | Square feet | Square meters | Typical use |
|---|---|---|---|
| 10 × 10 ft | 100 | 9.29 | small bedroom, home office |
| 10 × 12 ft | 120 | 11.15 | standard bedroom |
| 12 × 12 ft | 144 | 13.38 | large bedroom |
| 12 × 15 ft | 180 | 16.72 | primary bedroom, living room |
| 15 × 20 ft | 300 | 27.87 | great room, 1.5-car garage |
| 20 × 30 ft | 600 | 55.74 | 3-car garage, studio apartment |
| 2,000 sq ft home | 2,000 | 185.81 | median-range US single-family house |
| 1 acre | 43,560 | 4,046.86 | lot size; a quarter acre is 10,890 sq ft |
The acre row is worth a second look: 43,560 sq ft is exact, inherited from the old definition of a furlong (660 ft) times a chain (66 ft). It means a 2,000 sq ft house occupies about 4.6% of a one-acre lot, which is why acreage and house size read as such different kinds of big.
Worked example
Say a living room measures 14 ft 6 in by 12 ft 3 in and you are pricing vinyl plank at $4.75 per square foot. Convert the inches first: 6 in is 0.5 ft and 3 in is 0.25 ft, so the room is 14.5 × 12.25 = 177.63 square feet (177.625 exactly). That is 19.74 square yards, 16.50 square meters, and materials at list price come to 177.625 × 4.75 = $843.72.
Real orders add waste. At a 10% waste factor the quantity becomes 177.625 × 1.1 = 195.39 sq ft, and the material budget rises to $928.09. If the flooring ships in boxes covering 23.8 sq ft, you would round 195.39 up to nine boxes. Running the same room through the calculator in meters (4.42 × 3.73) lands within rounding of the same answer, which is a good spot check that a metric floor plan and your tape measure agree.
Measuring like a flooring estimator
Professionals measure the room's longest span wall to wall in both directions, including doorways and closet floors that will receive the same material, and they measure twice. Irregular rooms get split: an L shape becomes two rectangles, a bay window becomes its own small box, and each piece is calculated separately before adding. When a wall is not square, they take the larger of two measurements, because overestimating by a plank is an offcut while underestimating is a second delivery charge.
Waste factors are not padding for bad math, they cover unavoidable offcuts: 5 to 10% for straight layouts, 15% for diagonal or herringbone patterns, and more for tile with a repeating motif that must line up. Keep the leftover material after the job; matching a discontinued floor three years later is far harder than storing a box in the garage.
Frequently asked questions
How do I calculate square footage?
Measure the length and the width in feet and multiply them. A 12 ft by 15 ft bedroom is 12 × 15 = 180 square feet. If a measurement includes inches, convert them to a decimal first by dividing by 12: 14 ft 6 in is 14.5 ft. The calculator on this page does the unit conversion for you.
How do I measure an L-shaped or irregular room?
Split the floor into rectangles, calculate each one with length times width, and add the results. An L-shaped room that is a 12 × 10 section joined to a 6 × 8 section is 120 + 48 = 168 square feet. For angled or curved areas, box them into the smallest rectangle that contains them and accept a slight overestimate, which is the safe direction for ordering materials.
How do I convert square feet to square meters?
Multiply square feet by 0.0929. The factor is exact at 0.09290304 because a foot is defined as exactly 0.3048 meters and area squares that definition. A 2,000 sq ft home is 185.81 square meters. To go the other way, multiply square meters by 10.764.
How many square feet are in an acre?
Exactly 43,560 square feet. That comes from the acre's definition as one furlong by one chain, 660 ft × 66 ft. A quarter-acre lot is 10,890 sq ft, and a 2,000 sq ft house covers about 4.6% of a full acre.
What counts in a house's square footage?
Listings generally count finished, heated, above-grade living space. Garages, unfinished basements, attics and outdoor porches are usually excluded, though finished basements are often listed separately. Standards vary by market and appraiser, so when a listing number matters, ask what it includes before comparing homes on price per square foot.
How much flooring should I buy for my square footage?
Add a waste factor to the measured area: 5 to 10% for straightforward plank or tile layouts, and up to 15% for diagonal layouts or patterns that need matching. For a 178 sq ft room at 10% waste you would order about 196 sq ft. Whole boxes round you up further, since flooring sells in fixed coverage per box.
How do I convert square feet to square yards?
Divide by 9, because a yard is 3 feet and a square yard is 3 × 3 = 9 square feet. Carpet in the US is often quoted per square yard: a 180 sq ft bedroom is 20 square yards, so carpet at $22 per square yard costs about $440 for the room before padding and installation.