Square Footage Calculator
Estimates from your measurements. For a legal or appraisal figure, have the property measured to the standard your lender or county uses.
To find square footage, multiply length by width in feet. A room 12 ft 6 in by 10 ft is 12.5 × 10 = 125 square feet; with 10% extra for flooring waste, buy for about 137.5. Enter one room or add as many as you need below. Irregular rooms work too: break them into pieces and subtract any cutouts.
Square feet to square yards, square meters, and acres
| Square feet | Square yards | Square meters | Acres |
|---|---|---|---|
| 100 | 11.1 | 9.3 | 0.002 |
| 250 | 27.8 | 23.2 | 0.006 |
| 500 | 55.6 | 46.5 | 0.011 |
| 1,000 | 111.1 | 92.9 | 0.023 |
| 1,500 | 166.7 | 139.4 | 0.034 |
| 2,000 | 222.2 | 185.8 | 0.046 |
| 2,500 | 277.8 | 232.3 | 0.057 |
| 5,000 | 555.6 | 464.5 | 0.115 |
| 10,890 | 1,210.0 | 1,011.7 | 0.250 |
| 21,780 | 2,420.0 | 2,023.4 | 0.500 |
| 43,560 | 4,840.0 | 4,046.9 | 1.000 |
How to calculate square footage
Measure the length and width in feet and multiply them:
square feet = length (ft) × width (ft)
A room 14 ft long and 11 ft wide is 14 × 11 = 154 square feet. That is the whole method for any rectangle. Everything else on this page is about getting the measurements into feet, or breaking an awkward space into rectangles.
Square footage from feet and inches
Tape measures give you feet and inches, and you can't multiply those as they are: 12 ft 6 in is not 12.6 ft. Divide the inches by 12 and add the result to the feet. So 6 inches is 0.5 ft, and 12 ft 6 in is 12.5 ft. A room 12 ft 6 in by 10 ft 3 in is 12.5 × 10.25 = 128.1 square feet.
- 1 in = 0.08 ft
- 2 in = 0.17 ft
- 3 in = 0.25 ft
- 4 in = 0.33 ft
- 6 in = 0.5 ft
- 8 in = 0.67 ft
- 9 in = 0.75 ft
- 10 in = 0.83 ft
The calculator starts in feet + inches, so you can type the two numbers the way you read them off the tape.
Square footage from inches
If you measured everything in inches, multiply length × width to get square inches and divide by 144, because a square foot is 12 × 12 = 144 square inches. A 48 × 30 in countertop is 1,440 square inches, or exactly 10 square feet.
Multiple rooms and irregular shapes
To total several rooms, work out each one and add them up. The same trick handles any irregular space: split it into simple shapes, then add the pieces. Use one row per piece in the calculator, and it keeps a running total.
An L-shaped room, two ways
Take an L-shaped room that fits inside a 20 × 15 ft rectangle with a 6 × 5 ft corner missing. You can add two rectangles (20 × 10 ft plus 14 × 5 ft = 200 + 70) or take the full rectangle and subtract the corner (300 − 30). Both give 270 square feet. Set a row to Subtract for the second method. It also works for a closet you aren't flooring, a kitchen island, or a fireplace hearth.
Formulas for other shapes
- Triangle: base × height ÷ 2. Height is measured square to the base, not along the sloped side.
- Circle: 3.1416 × (diameter ÷ 2)². A 10 ft round patio is about 78.5 square feet.
- Trapezoid (a room with one angled wall): (side A + side B) ÷ 2 × height. Sides A and B are the two parallel walls, and height is the distance between them. A room with parallel walls of 10 ft and 14 ft, 8 ft apart, is 96 square feet.
Square footage of a house
What you get from adding up the rooms is not the number on a listing or an appraisal, and the difference is normal. In the US, Fannie Mae and Freddie Mac rely on the ANSI Z765 standard for one-unit homes. As summarized by Opendoor's guide, that standard differs from a room-by-room tape measure in several ways:
- It measures to the exterior face of the walls, not the inside of the drywall, which can add roughly 5–7%.
- Finished space counts only with a ceiling of at least 7 ft. Under a sloped ceiling, 5 ft is allowed as long as at least half the floor area has the full 7 ft.
- Garages don't count, even finished ones.
- Below-grade space, such as a finished basement, is reported on a separate line and not added to the above-grade total.
Use this calculator for materials and planning. If a loan, a sale, or a tax assessment depends on the figure, ask which measuring standard applies, because county records and listings don't all follow the same one. ANSI Z765 itself is a paid document, so check any detail that matters against the published standard or with your appraiser.
Using square footage to buy materials
Flooring and tile
Measure the floor you will cover, then add extra for cuts and breakage. Around 10% is typical for straight layouts, 15% for diagonal, and up to 20% for herringbone or chevron. Round up to whole boxes, then check the coverage printed on the box, since it varies by product. The tile calculator turns your area into tiles, boxes, and grout. Carpet is often priced by the square yard, so divide square feet by 9 before you compare quotes.
Walls and paint
For a wall, multiply its length by its height. For a whole room, add the lengths of all the walls and multiply by the ceiling height: a 12 × 10 ft room with 8 ft ceilings has (12 + 10 + 12 + 10) × 8 = 352 square feet of wall. Add a Subtract row for each large door or window. Paint coverage is printed on the can, so divide your wall area by that figure and multiply by the number of coats, or use the paint calculator. The drywall calculator uses the same wall area to count sheets.
Anything sold by volume
Gravel, soil, mulch, and concrete all start from square footage and add a depth. The shortcut is cubic yards = square feet × depth in inches ÷ 324, or use the cubic yard calculator.
Converting square feet
- Square feet to square yards: divide by 9.
- Square feet to square meters: multiply by 0.0929. Going the other way, 1 square meter is 10.76 square feet.
- Square feet to acres: divide by 43,560. A quarter acre is 10,890 square feet.
- Square inches to square feet: divide by 144.
Square feet measure area and linear feet measure length, so one can't be converted to the other without a second dimension. To get square feet from linear feet of boards, multiply by the board width in feet: 100 linear feet of 6 in wide board is 50 square feet.
Common mistakes
- Reading inches as decimals. 10 ft 6 in is 10.5 ft, not 10.6. On a large room the error adds up to several square feet.
- Assuming the room is square. Older rooms often aren't. Measure both ends of each wall and use the longer number when you are buying materials.
- Adding waste to a measured area you then quote. Keep the two apart: the total is what the room measures, and the waste figure is what you buy for.
- Forgetting doorways and closets. Flooring usually runs through a doorway and into closets, so measure those as their own rows.
Frequently asked questions
How do I calculate square footage?
Multiply length by width, with both in feet. A 15 × 12 ft room is 180 square feet. For irregular spaces, split the area into rectangles, work out each one, and add them together.
How do I calculate square footage with feet and inches?
Divide the inches by 12 and add them to the feet before you multiply. A room 12 ft 6 in by 10 ft 3 in is 12.5 × 10.25 = 128.1 square feet.
How do I calculate square feet from inches?
Multiply length by width in inches and divide by 144. A 48 × 30 in surface is 1,440 square inches, which is 10 square feet.
How do I find the square footage of multiple rooms?
Work out each room separately and add the results. In the calculator, add one row per room and the total updates as you go. Subtract rows take out anything you are not covering, such as a closet.
How do I calculate the square footage of an irregular shape?
Divide it into rectangles, triangles, and circles, find each area, and add them up. An L-shaped room is two rectangles, or one big rectangle minus the missing corner.
How do I calculate the square footage of a house?
For planning, add up the area of every room plus hallways and closets. Appraisers measure differently: the ANSI Z765 standard measures to the exterior of the walls and reports below-grade space separately, so an official figure often differs from your total.
How do I calculate the square footage of a wall?
Multiply the wall length by its height. A 12 ft wall with an 8 ft ceiling is 96 square feet. Subtract large openings if you are working out paint or drywall.
How many square feet are in a square yard?
Nine, because a square yard is 3 ft × 3 ft. To convert square feet to square yards, divide by 9. That is useful for carpet, which is often priced by the yard.
How many square feet are in an acre?
43,560. A quarter acre is 10,890 square feet and a half acre is 21,780. Divide square feet by 43,560 to get acres.
How much extra flooring should I buy?
About 10% for a straight layout, 15% for diagonal, and up to 20% for herringbone or chevron. Use the waste field for this; the measured total stays visible next to it.
Related calculators
Sources
- NIST Guide to the SI, Appendix B: Conversion FactorsNational Institute of Standards and Technology (NIST)Exact relationships: 1 ft = 0.3048 m, so 1 ft² = 0.09290304 m²; 1 acre = 43,560 ft².
- How to Measure Square FootageOpendoorPlain-language summary of ANSI Z765: exterior measurement, ceiling-height rules, garages, and below-grade space.
- ANSI Z765 and the New UAD 3.6: What Appraisers Need to KnowMcKissock LearningBackground on Fannie Mae and Freddie Mac adopting ANSI Z765 for one-unit homes.
- Tile CalculatorInch CalculatorWaste allowances of 10% for straight and 15% for diagonal layouts.
- How Much Tile Do I Need?Bob VilaUp to 20% extra for complex patterns against about 10% for standard layouts.