How do I calculate square footage of a room?

Measure the length and width of the room in feet, then multiply: Length x Width = Square Feet. For a 15 x 12 ft room, that is 15 x 12 = 180 sq ft. If your tape measure shows inches, convert to decimal feet first by dividing the inches by 12 (e.g., 6 inches = 0.5 ft).

How do I calculate square footage of an L-shaped room?

Divide the L-shape into two rectangles at the inside corner. Calculate the area of each rectangle separately (length x width), then add them together. For example, a 20 x 12 ft section (240 sq ft) plus a 10 x 8 ft section (80 sq ft) equals 320 sq ft total. A simple sketch helps avoid mistakes.

What is the difference between square feet and square yards?

One square yard equals 9 square feet (3 ft x 3 ft = 9 sq ft). Carpet, sod, and some specialty floorings are sold by the square yard. To convert square feet to square yards, divide by 9. For example, 180 sq ft divided by 9 equals 20 sq yd. Our calculator shows both units automatically.

How much extra material should I order?

For most flooring and wall covering projects, add 10% to your calculated square footage. This waste factor accounts for cuts at walls, corners, and defects. For tile, diagonal installations, or patterned materials, add 15%. For sod, add only 5%. Never order less than your calculated area plus the appropriate waste factor.

Do closets count in square footage?

Yes, for real estate listings in the US, finished closet floor area is included in the total square footage. For material ordering, include closets if you plan to install the same flooring inside them. For paint or wallpaper, closets are typically excluded from wall area calculations unless you plan to finish them.

How do I convert inches to decimal feet?

Divide the inches by 12 to get the decimal equivalent. For example, 15 ft 6 in = 15 + (6 / 12) = 15.5 ft. Common conversions: 3 in = 0.25 ft, 6 in = 0.5 ft, 9 in = 0.75 ft. Our calculator accepts decimal feet input directly for convenience.

Is square footage the same as floor area?

For single-story buildings, yes. For multi-story buildings, square footage typically refers to the total finished floor area across all levels, while floor area usually refers to a single level. In real estate listings, square footage includes all finished, habitable spaces above grade but typically excludes basements, garages, and unfinished attics.

Square Footage Calculator

Calculate the square footage of any room or space in seconds.

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Square Footage Calculator

Length(ft)

Width(ft)

For multiple rooms or irregular spaces, calculate each rectangular section separately and add the results together. To convert inches to decimal feet, divide the inches by 12 (for example, 15 ft 6 in becomes 15.5 ft). Always add 10-15% waste before ordering materials.

What This Calculator Does

The Square Footage Calculator computes the total area of any rectangular or square space in square feet - the standard unit for construction, flooring, paint, and real estate in the United States. Simply enter the length and width of a room, house, lot, or workspace, and get the exact area in seconds.

Square footage is the foundation of nearly every construction estimate. Flooring, paint, concrete, tile, drywall, and siding are all priced per square foot. Knowing the exact area before you shop or contact contractors ensures you order the right amount of material and get accurate quotes. A 10% measurement error on a 2,000 sq ft project can mean $200-$500 in wasted material or emergency supply runs.

Use this calculator for any rectangular space: rooms, additions, decks, patios, lots, driveways, or wall sections. For irregular shapes, divide the area into rectangles, calculate each, and add them together - or use our Area Calculator for more shape options.

How to Use

Measure the length of the space in feet using a tape measure. For large areas, use a measuring wheel or reference property plans.
Measure the width in feet at the widest point. For irregular rooms, measure at multiple points and use the average.
Enter both values into the calculator fields above. Use decimal values for inches (e.g., 12.5 for 12 ft 6 in).
Click "Calculate" to get the total square footage, square yards, and square meters.
Use the "Copy Result" button to save your square footage for supplier quotes or material calculators on this site.

How to Calculate Square Footage

Calculating square footage is straightforward for any rectangular area. Follow these steps:

Measure the length. Use a tape measure to find the longest dimension of the room or area in feet. Measure from wall to wall at the floor level, not at baseboard height.
Measure the width. Find the shorter dimension in feet. If your measurement includes inches, divide the inches by 12 to get a decimal value (e.g., 6 inches = 0.5 ft, so 12 ft 6 in = 12.5 ft).
Multiply. Area in square feet = Length x Width.
For L-shaped rooms. Divide the space into two rectangles at the inside corner, calculate each separately, and add the results.

This calculation works for any rectangular room or area including bedrooms, living rooms, kitchens, garages, decks, patios, lawns, and building lots. For non-rectangular shapes, refer to the formulas section below.

Practical Measurement Tips

Tape measure accuracy. A standard tape measure is accurate to about +/- 1/8 inch over 25 feet. For rooms longer than 30 feet, consider using a laser distance measure for greater precision.
Measure at the floor. Always measure at floor level rather than at baseboard height. Walls can bow slightly, and baseboards may not be perfectly parallel to the floor.
Include everything. Measure into closets, bay windows, alcoves, and other attached spaces. Even if you do not plan to install flooring in these areas, they count toward the total square footage for property listings and permit applications.
Double-check. Measure each dimension twice. A transcription error of 6 inches on a 20-ft wall creates a 10 sq ft error, which can lead to ordering one extra box of flooring or running short.
Draw a sketch. For irregular rooms, sketch the layout on graph paper and divide into rectangles. Label each rectangle with its dimensions before calculating.

Worked Examples

Living Room Flooring

A 15 x 18 ft living room with standard hardwood flooring installation.

→Calculate the floor area: 15 ft x 18 ft = 270 sq ft.
→Apply 10% waste factor for hardwood (cuts at walls, end joints): 270 x 1.10 = 297 sq ft.
→At $4.50 per sq ft for LVP materials: 297 x $4.50 = $1,337 material cost.

Result: 270 sq ft room area, 297 sq ft to order with waste.

For diagonal hardwood installation, use 15% waste instead of 10%.

Use our Flooring Cost Calculator

Paint Estimation for a Bedroom

A 12 x 14 ft bedroom with 9-ft ceilings, one standard door (21 sq ft) and two windows (15 sq ft each).

→Calculate wall perimeter: 2 x (12 + 14) = 52 ft.
→Gross wall area: 52 ft x 9 ft ceiling = 468 sq ft.
→Subtract openings: 468 - 21 (door) - 30 (2 windows) = 417 sq ft net wall area.
→At 350 sq ft per gallon coverage: 417 / 350 = 1.19 gallons per coat.
→Round up to 2 gallons for one coat, 4 gallons for two coats.

Result: 417 sq ft net wall area needing 2 gallons (1 coat) or 4 gallons (2 coats).

Always round up to the nearest gallon. Paint calculators typically assume smooth primed surfaces; rough or textured walls reduce coverage by 20-30%.

Use our Paint Calculator

Tile for a 9 x 11 ft Bathroom

Standard bathroom floor with ceramic tile installation.

→Calculate floor area: 9 ft x 11 ft = 99 sq ft.
→Subtract vanity/toilet area: approximately 5 sq ft for a standard toilet and vanity footprint.
→Net tile area: 94 sq ft.
→Apply 15% waste for tile (cuts around fixtures, breakage): 94 x 1.15 = 108 sq ft.
→Round up to order: 110 sq ft of tile.

Result: Approximately 110 sq ft of tile to order for a 99 sq ft bathroom.

Tile waste can reach 20% for diagonal layouts, herringbone patterns, or large-format tiles. Always buy extra from the same batch to ensure color consistency.

Use our Tile Calculator

L-Shaped Living and Dining Room

An L-shaped open-concept space combining a 20 x 14 ft living area and a 12 x 10 ft dining area.

→Divide the L-shape into two rectangles at the inside corner.
→Rectangle A (living): 20 ft x 14 ft = 280 sq ft.
→Rectangle B (dining): 12 ft x 10 ft = 120 sq ft.
→Total area: 280 + 120 = 400 sq ft.
→Apply 10% waste for laminate flooring: 400 x 1.10 = 440 sq ft to order.

Result: 400 sq ft total living/dining area; 440 sq ft to order with waste.

Always sketch the room first. Divide at the inside corner using the fewest possible rectangles. Each extra rectangle increases the chance of a measurement mistake.

Formulas for Different Shapes

Square footage formulas for common shapes used in construction and landscaping.
Shape	Formula	Example	Common Use
Rectangle or Square	`L x W`	15 x 12 = 180 sq ft	Rooms, slabs, lots, walls
Right Triangle	`1/2 x B x H`	1/2 x 10 x 8 = 40 sq ft	Corner lots, roof sections, attic floors
Circle	`pi x r squared`	3.14 x 5 x 5 = 78.5 sq ft	Round patios, gazebos, silo bases
Trapezoid	`1/2 x (B1 + B2) x H`	1/2 x (10 + 14) x 6 = 72 sq ft	Irregular lots, angled walls, yard sections
Ellipse	`pi x a x b`	3.14 x 6 x 4 = 75.4 sq ft	Oval pools, elliptical patios, decorative beds

Waste Factors by Material

Always order more than your exact calculated quantity. Material suppliers typically do not accept returns on cut or opened materials. The waste factor accounts for cuts at walls, corners, defects, and installation error.

Standard waste factors for common construction materials ordered by square footage.
Material	Waste Factor	Notes	Related Calculator
Hardwood flooring (straight)	10%	End cuts at walls per NWFA guidelines	Flooring Cost Calculator
LVP / Laminate (straight)	10%	Staggered joints and end cuts	Flooring Cost Calculator
Hardwood / Laminate (diagonal)	15%	45-degree cuts waste more at perimeter	Flooring Cost Calculator
Ceramic / Porcelain tile	10-15%	Cuts, breakage, and grout joint waste	Tile Calculator
Carpet	10%	Seam placement and roll width limitations	Flooring Cost Calculator
Wallpaper	15-20%	Pattern repeat waste at seams	Wallpaper Calculator
Roofing shingles	10-15%	Hip, ridge cuts, and starter strips	Roofing Material Calculator
Sod / turf	5%	Trimming at borders and around curves	Sod Calculator

Square Footage by Project Type

How square footage is used across different construction and renovation projects.
Project	What to Measure	Unit	Key Note	Related Tool
Flooring installation	Room floor area (L x W)	Square feet	Add 10% waste; diagonal adds 15%	Flooring Cost Calculator
Wall painting	2 x (L + W) x height minus openings	Sq ft per gallon	350-400 sq ft per gallon; multiply by coats	Paint Calculator
Wall tile / backsplash	Wall area minus cabinets and openings	Square feet	Add 10-15% for cuts around fixtures	Tile Calculator
Roofing replacement	Sloped roof surface area (not footprint)	Squares (100 sq ft)	Multiply footprint by pitch multiplier first	Roof Pitch Calculator
Insulation (batt)	Wall or ceiling cavity area	Sq ft per bag or roll	Check R-value requirements for your climate zone	Insulation Calculator
Drywall installation	Wall and ceiling area minus openings	4 x 8 sheets (32 sq ft)	Add 10% for cuts and waste	Drywall Calculator
Sod / grass seed	Lawn area (exclude beds, paths, structures)	Sq ft per pallet	Sod pallets cover 400-500 sq ft each	Sod Calculator
Mulch / topsoil	Bed area (L x W)	Cubic yards (volume)	Need area plus depth to get cubic yards	Mulch Calculator

Reference Table

Common room sizes and their square footage - 2026 reference
Room Size	Square Footage	Typical Use	Paint (1 coat)
10 x 10 ft	100 sq ft	Small bedroom	~0.25 gal
12 x 12 ft	144 sq ft	Standard bedroom	~0.36 gal
12 x 16 ft	192 sq ft	Living room	~0.48 gal
20 x 20 ft	400 sq ft	2-car garage	~1 gal
20 x 30 ft	600 sq ft	Studio apartment	~1.5 gal
50 x 100 ft	5,000 sq ft	Building lot	N/A

How We Calculate

Basic Rectangle Formula

The core formula used by this calculator is the standard geometric area formula for rectangles: Area = Length x Width. Both dimensions must be in the same unit (feet). If you have measurements in feet and inches, convert the inches to a decimal by dividing by 12 before entering.

Unit Conversions

After computing the area in square feet, the calculator converts to three additional units using these exact conversion factors:

Square yards = Square feet / 9 (since 1 yard = 3 ft, 1 sq yd = 9 sq ft)
Square meters = Square feet x 0.09290304 (per the 1959 international foot definition)
Square inches = Square feet x 144 (since 1 sq ft = 12 x 12 = 144 sq in)

Waste Factor

The calculator displays the raw square footage without a built-in waste factor. To determine the quantity to order, multiply the raw area by (1 + waste percentage). For example, 200 sq ft with 10% waste = 200 x 1.10 = 220 sq ft to order. Use the waste factor table above to select the appropriate percentage for your material.

References and Data Sources

NIST - US Customary Unit Definitions (Square Foot)

The square foot is defined as the area of a square with sides of exactly 1 foot (0.3048 meters), per the international foot definition established by the International Yard and Pound Agreement of 1959. All conversion factors used in this calculator (sq ft to sq yd, sq m, sq in) derive from this exact definition. National Institute of Standards and Technology, NIST HB 44.

NWFA - National Wood Flooring Association Installation Guidelines

Industry-standard waste factors for hardwood flooring: 10% for straight-lay installations and 15% for diagonal installations. These allowances are used by professional flooring installers across the United States and are referenced in the worked examples above.

Paint Industry Standard Coverage Rates

Interior latex paint coverage of 350-400 square feet per gallon is the industry-published spread rate for smooth, primed surfaces. Actual coverage varies by paint brand, sheen level, surface texture, and application method. Always verify with the specific paint manufacturer product data sheet before purchasing.

TCNA - Tile Council of North America Handbook

Ceramic and porcelain tile installation waste factors of 10-15% for standard layouts, as referenced in the waste factor table and worked examples. Waste percentage depends on tile size, layout pattern, and room shape complexity.

All references are used for general estimation guidance only. BuildCalcHub does not claim certification, endorsement, or partnership with any listed organization. Always consult a licensed professional for your specific project requirements.

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