Square Footage Calculator

Use this Square Footage Calculator to calculate square feet for a room, floor, wall, house project, yard, patio, or other space. Enter measurements in feet and inches, calculate several rooms together, measure irregular areas, convert between square units, and estimate material quantities or project costs from the finished square footage.

For a basic rectangular area, measuring square footage is as simple as multiplying length by width. Real projects are often more complicated, though, so the calculator also handles multiple rooms, walls with doors and windows, circles, triangles, L-shaped areas, waste allowances, square-foot conversions, and cost per square foot.

How to Use the Square Footage Calculator

Choose the calculator mode that matches what you are measuring. For a normal bedroom, living room, floor, patio, deck, section of lawn, or other rectangular space, use Room / Floor. Enter the length and width using the separate feet and inches boxes and press Calculate Square Footage.

The main result shows the measured area in square feet. The calculator also converts that answer into square metres, square yards, square inches, and acres automatically.

If you are planning a project rather than simply measuring an area, you can add a waste allowance, coverage per package, and cost per square foot. For example, if a room contains 200 square feet and you add 10% extra, the calculator will show 220 square feet of material. If each box covers 22 square feet, it will calculate that 10 boxes are required.

Room / Floor Mode

Use this mode for one square or rectangular space. Measurements can include whole feet and additional inches, so a room measuring 12 feet 6 inches by 10 feet 3 inches can be entered without converting the measurements yourself.

Multiple Rooms Mode

Use Multiple Rooms when you are measuring several bedrooms, an entire flooring project, multiple offices, an apartment, or other spaces that need to be added together. Add as many as 20 rectangular sections and the calculator totals their areas.

Walls Mode

Walls mode calculates the area of all four walls in a rectangular room from the room length, width, and wall height. You can then subtract the area occupied by doors and windows. This is useful for paint, wallpaper, panelling, drywall, and other wall-covering projects.

Shapes / Irregular Mode

Not every area is a rectangle. Shapes mode includes rectangles, triangles, circles, and L-shaped areas. An L-shaped space is calculated as one large rectangle minus its rectangular cutout.

Area Converter

The conversion tool converts square feet, square inches, square yards, square metres, square centimetres, acres, and hectares. It is useful when your measurements or material specifications use a different area unit than the project.

How to Calculate Square Feet

To calculate square feet for a rectangular area, measure its length and width in feet and multiply the two measurements together.

If a room is 12 feet long and 10 feet wide:

The room contains 120 square feet of floor area.

This same length-times-width formula works for any rectangular surface when both measurements use feet. It can be used for rooms, floors, rectangular walls, patios, decks, yards, garden beds, driveways, concrete slabs, rugs, countertops, and many construction materials.

If you want to calculate geometric areas in many other shapes and units, use the Area Calculator. That tool also covers circles, trapezoids, parallelograms, ellipses, surface area, and other geometry calculations.

Square Footage Formula

The formula depends on the shape of the area. Most household square-footage measurements are rectangular, which is why length × width is the formula people use most often.

When an irregular room can be divided into several rectangles, triangles, or other simple shapes, calculate each section and add the results. Home-improvement measurement guides commonly use this approach for rooms that are not simple rectangles. Home Depot's square-footage guide also recommends dividing complicated spaces into separate measurable sections.

How to Measure the Square Footage of a Room

Start with a tape measure and measure from one wall to the opposite wall. Record the longest dimension as the room length and the other dimension as the width. For a rectangular room, multiply the two measurements.

1. Measure the room length from wall to wall.
2. Measure the room width from wall to wall.
3. Convert any extra inches to part of a foot, or enter them directly into the calculator.
4. Multiply the length by the width.
5. Add a waste allowance if the measurement is being used to purchase materials.

For example, a bedroom measuring 14 feet long by 12 feet wide contains:

14 × 12 = 168 square feet.

A 20-foot-long living room that is 15 feet wide contains 300 square feet. A 10-by-10 room contains exactly 100 square feet.

How to Calculate Square Feet From Feet and Inches

Real rooms frequently do not measure an exact number of feet. A wall might be 12 feet 6 inches long or 9 feet 9 inches wide. Because there are 12 inches in a foot, divide the extra inches by 12 before multiplying.

For example, 6 inches is 0.5 foot because 6 ÷ 12 = 0.5. Therefore 12 feet 6 inches equals 12.5 feet.

Nine inches is 0.75 foot, so 10 feet 9 inches equals 10.75 feet.

A room measuring 12 ft 6 in by 10 ft 9 in therefore contains:

12.5 × 10.75 = 134.375 square feet.

The calculator performs this conversion automatically. Enter the whole feet and remaining inches into their separate boxes instead of converting them manually.

Do Not Treat Inches as Decimal Feet

One of the easiest square-footage mistakes is treating inches as though they were decimal fractions of a foot. Six inches is not 0.6 feet. It is 0.5 feet. Three inches is 0.25 foot, not 0.3 foot.

How to Calculate Square Footage of Multiple Rooms

To calculate the square footage of several rooms, calculate each room separately and add the results. Do not simply multiply the home's longest overall dimensions unless the building is a perfect rectangle and those measurements represent the area you actually need.

Suppose you need flooring for three rooms:

• Living room: 15 × 12 = 180 ft²
• Bedroom: 12 × 10 = 120 ft²
• Hallway: 12 × 4 = 48 ft²

Add the three areas:

180 + 120 + 48 = 348 square feet.

If you are ordering flooring and want 10% extra material, multiply 348 by 1.10. The project quantity becomes 382.8 square feet before accounting for package sizes.

How to Calculate the Square Footage of a House

The phrase “square footage of a house” can mean different things depending on why you need the number. If you are ordering flooring, you generally want the surface area of the floors that will actually receive the new material. Measure each included room and add the areas.

Official residential living-area measurements used for real estate, appraisal, taxation, insurance, or building documentation can follow specific standards and rules about which finished spaces are included. A DIY room measurement should not automatically be treated as an official reported living-area figure.

For a renovation budget based on the size of a house or room, you can also compare your result with the Home Renovation Cost Calculator.

How to Calculate Square Footage of an Irregular Room

An irregular floor plan is usually easiest to calculate by dividing it into simple shapes. Draw a rough sketch of the space, mark the measurements, divide the room into rectangles or triangles, calculate each section, and then add the pieces.

For example, imagine one part of a room measures 12 × 10 feet and an additional rectangular section measures 6 × 4 feet:

• Main section: 12 × 10 = 120 ft²
• Additional section: 6 × 4 = 24 ft²
• Total: 120 + 24 = 144 ft²

This approach works for many L-shaped, T-shaped, stepped, or offset rooms.

How to Calculate an L-Shaped Room

There are two convenient methods for an L-shaped area. You can split the L into two rectangles and add them, or calculate one large outside rectangle and subtract the missing rectangular section.

The calculator's L-shape option uses the subtraction method.

If the outer rectangle is 15 × 12 feet, its area is 180 square feet. If the missing corner is 5 × 4 feet, that cutout contains 20 square feet.

180 − 20 = 160 square feet.

Square Footage of a Triangle

A triangular area is calculated using one-half of the base multiplied by the perpendicular height.

Triangle Area = ½ × Base × Height

A triangular area with a 12-foot base and a perpendicular height of 10 feet contains:

½ × 12 × 10 = 60 square feet.

The height must be measured perpendicular to the base. A sloping side is not necessarily the height.

Square Footage of a Circle

For circular patios, landscaping areas, round rooms, fire-pit zones, pools, or other circles, use the area formula πr². The radius is half the diameter.

A 10-foot-diameter circle has a 5-foot radius:

π × 5² = approximately 78.54 square feet.

How to Calculate Wall Square Footage

Wall area is useful when estimating paint, wallpaper, drywall, panelling, insulation, tile, or other wall coverings. For one plain rectangular wall, multiply wall width by wall height.

A 12-foot-wide wall with an 8-foot height contains:

12 × 8 = 96 square feet.

For all four walls of a rectangular room, first calculate the room perimeter and multiply it by the wall height:

A 12 × 10 room with 8-foot walls has a perimeter of 44 feet. Multiply 44 by 8 to get 352 square feet of gross wall area.

Subtract Doors and Windows

If you need the net surface that will actually receive paint, wallpaper, tile, or another finish, calculate the area of openings and subtract them from the gross wall area.

For example, suppose the 352-square-foot wall area contains one 3 × 6.67-foot door and two 3 × 4-foot windows. The approximate door area is 20.01 square feet and the windows occupy another 24 square feet.

The net wall area is approximately:

352 − 20.01 − 24 = 307.99 square feet.

How to Calculate Square Footage for Flooring

For flooring, measure each floor area that will receive the new material. Calculate the square footage of every room or section and add them together.

The measured floor area is not always the same as the amount of flooring you need to buy. Cuts, damaged pieces, layout, pattern matching, and future repairs can require additional material. The appropriate waste percentage depends on the product and installation.

The calculator lets you enter any waste allowance instead of assuming one percentage is correct for every material.

How Much Flooring Do I Need?

First calculate the floor area, then add any planned waste allowance. Finally, divide the adjusted area by the coverage printed on each box or package and round up to the next whole box.

Suppose your measured area is 500 square feet and you add 10%:

500 × 1.10 = 550 square feet.

If one box covers 23 square feet:

550 ÷ 23 = 23.91 boxes.

Because you cannot normally buy 0.91 of a box, round up to 24 boxes.

Square Footage for Tile

Tile calculations start with the same surface area. Measure the floor or wall section, calculate the square footage, then consider the tile pattern, cuts, breakage, and spare pieces.

A diagonal pattern or complicated room may create more offcuts than a straightforward layout. Use the calculator's custom waste percentage instead of assuming every project requires exactly the same allowance.

Square Footage for Paint

For paint, calculate the wall surface rather than the floor area. Walls mode can subtract doors and windows and return the net square footage.

Once you know the wall area, check the coverage stated on the specific paint container. Coverage can vary based on paint type, surface texture, colour change, application method, and number of coats.

Square Footage for Concrete

Square feet describes surface area, but concrete orders require volume because the slab has thickness. First calculate the slab length and width, then include the planned depth to determine cubic feet or cubic yards.

For slab, footing, column, or other concrete-volume calculations, use the Concrete Calculator.

Square Footage for a Patio or Pergola

A rectangular patio or pergola footprint uses the same length × width formula. A 12 × 16 outdoor structure covers 192 square feet, while a 20 × 20 structure covers 400 square feet.

If you are estimating an outdoor structure rather than just its area, the Pergola Cost Calculator uses square footage along with materials, installation, roofing, and other options to estimate project cost.

Square Foot Conversions

Square feet can be converted into other area units, but remember that area conversion is different from converting ordinary feet or inches. A linear foot measures distance. A square foot measures two-dimensional area.

Square Inches to Square Feet

There are 144 square inches in one square foot because a square measuring one foot by one foot measures 12 inches × 12 inches.

To convert square inches to square feet:

For example:

1,440 in² ÷ 144 = 10 ft².

Square Feet to Square Inches

To convert square feet to square inches, multiply by 144.

10 ft² × 144 = 1,440 in².

Square Yards to Square Feet

One square yard contains 9 square feet. Multiply square yards by 9 to convert to square feet.

20 yd² × 9 = 180 ft².

Square Feet to Square Yards

Divide square feet by 9.

450 ft² ÷ 9 = 50 yd².

Square Metres to Square Feet

One square metre equals approximately 10.7639 square feet. Multiply square metres by approximately 10.7639 to convert to square feet.

For example, 20 square metres is approximately 215.28 square feet.

Square Feet to Square Metres

Divide square feet by approximately 10.7639, or multiply by approximately 0.092903.

A 1,000-square-foot area is approximately 92.90 square metres.

How Many Square Feet Are in an Acre?

There are 43,560 square feet in one acre.

To convert acres to square feet, multiply the number of acres by 43,560. A half-acre contains 21,780 square feet, while two acres contain 87,120 square feet.

Common Dimensions and Square Footage

The following table answers common dimension searches quickly. Each result assumes a rectangle measured in feet.

How Many Square Feet Is a 10 × 10 Room?

A 10-foot by 10-foot room contains 100 square feet. Multiply 10 by 10.

How Many Square Feet Is a 12 × 12 Room?

A 12-foot by 12-foot room contains 144 square feet.

How Many Square Feet Is 12 × 20?

A rectangular area measuring 12 feet by 20 feet contains 240 square feet.

How Many Square Feet Is 20 × 20?

A 20-foot by 20-foot square contains 400 square feet.

How Many Square Feet Is 30 × 30?

A 30-foot by 30-foot area contains 900 square feet.

What Does 100 Square Feet Look Like?

Square footage describes area, not one specific set of dimensions. A 10 × 10 room is 100 square feet, but so is a 20 × 5 rectangle or a 25 × 4 area.

Knowing only the square footage does not tell you the exact room shape. Many different length-and-width combinations can produce the same area.

What Does 1,000 Square Feet Mean?

An area of 1,000 square feet could be a 25 × 40-foot rectangle, a 20 × 50-foot rectangle, or many other combinations. Square footage tells you the amount of two-dimensional area, not the exact dimensions.

How to Calculate Cost Per Square Foot

If a product or project is priced by the square foot, multiply the required square footage by the price per square foot.

If flooring costs $4.50 per square foot and your material requirement is 550 square feet:

550 × $4.50 = $2,475.

The calculator includes an optional cost-per-square-foot field so you can combine the area and material estimate in one calculation.

Measured Area vs. Material Area

These two numbers should not always be treated as identical. Measured area is the actual mathematical surface calculated from your dimensions. Material area is the amount you intend to purchase after adding cuts, waste, pattern requirements, breakage, or spare material.

For example, a floor can measure exactly 400 square feet while the planned material quantity is 440 square feet after a 10% allowance.

If you need to calculate a different percentage allowance, you can also use the Percentage Calculator.

Common Square Footage Mistakes

• Mixing feet and inches: Convert measurements to a consistent unit before multiplying.
• Treating inches as decimal feet: Six inches is 0.5 foot, not 0.6 foot.
• Forgetting irregular sections: Divide unusual rooms into simpler measurable areas.
• Using floor area for walls: Wall coverings require wall surface area, not floor square footage.
• Confusing square feet and linear feet: They measure different things.
• Forgetting openings: Doors and windows can be deducted when calculating net wall coverage.
• Buying exactly the measured amount: Some installations require additional material for cuts or waste.
• Rounding too early: Keep precise measurements through the calculation and round the final result.

Square Foot vs. Linear Foot

A linear foot measures length. A square foot measures area. They cannot be converted directly unless you know another dimension.

For example, a board that is 10 linear feet long could cover very different square footage depending on its width. A 10-foot-long material that is 1 foot wide covers 10 square feet, while the same length at 6 inches wide covers only 5 square feet.

Square Foot vs. Foot

One foot is a measurement of distance. One square foot is an area measuring one foot long by one foot wide.

This difference explains why you cannot convert a measurement such as 15 feet directly into square feet without knowing the width or another dimension.

Why Accurate Square Footage Matters

Square footage is used throughout construction, renovation, flooring, painting, landscaping, real estate, heating and cooling, furniture planning, and material purchasing.

An error of only a few percent can become significant on a large project. Underestimating can leave you short of materials in the middle of the job, while a large overestimate can result in unnecessary expense.

Measure carefully, check unusual sections separately, and verify product coverage before purchasing.

Square Footage Examples

Example 1: 10 × 14 Bedroom

A bedroom measures 10 feet wide by 14 feet long.

10 × 14 = 140 ft².

Example 2: 15 × 18 Living Room

15 × 18 = 270 ft².

Example 3: Room With Inches

A room measures 13 ft 6 in by 11 ft 3 in. Convert the dimensions to 13.5 feet and 11.25 feet.

13.5 × 11.25 = 151.875 ft².

Example 4: Circle

A circular patio is 16 feet across. Its radius is 8 feet.

π × 8² ≈ 201.06 ft².

Example 5: L-Shaped Floor

An outer rectangle measures 20 × 15 feet, while a 6 × 5-foot section is missing.

20 × 15 = 300 ft².

6 × 5 = 30 ft².

300 − 30 = 270 ft².

Example 6: Flooring With Waste

A project measures 750 square feet. A 10% allowance adds 75 square feet.

Total planned material = 825 ft².

Why Use a Square Footage Calculator?

• Calculate square feet without doing the multiplication manually.
• Enter measurements using feet and inches.
• Add multiple rooms together.
• Calculate total wall surface.
• Subtract doors and windows from wall area.
• Measure circles and triangular areas.
• Calculate L-shaped rooms.
• Convert square inches to square feet.
• Convert square metres, square yards, acres, and hectares.
• Add custom material waste.
• Calculate packages or boxes needed.
• Estimate project cost from price per square foot.
• Use the calculator on mobile while measuring a room.

Square Footage Calculator Frequently Asked Questions

Final Thoughts

Square footage is one of the most useful measurements in home improvement, construction, flooring, painting, landscaping, and everyday space planning. For a rectangular area, the calculation is simply length multiplied by width, but actual projects often involve inches, several rooms, irregular shapes, openings, material waste, package sizes, and different units.

Use Room / Floor mode for a single rectangular area, Multiple Rooms when several spaces need to be added together, Walls mode for paint and wall coverings, Shapes mode for circles, triangles and L-shaped spaces, or Area Converter when you already know the area but need a different unit. Once you have the measured square footage, add the appropriate project allowance and material information to estimate how much you need to buy.