Square Footage Calculator
Calculate room area and total square footage for any space
Square Footage Calculator
How to Use This Calculator
Select the shape of the area you're measuring from the dropdown: rectangle (most common for rooms and yards), circle (for round patios or gazebos), triangle (for irregularly shaped yards or gables), or complex (for L-shaped or multi-section areas). Rectangle is the most straightforward calculation. For irregular spaces, break them into multiple simple shapes, calculate each separately, and sum the totals. The calculator handles the geometric formulas automatically—you simply input the required dimensions.
For rectangular areas, measure length and width in feet using a tape measure. Measure along the longest dimension for length, perpendicular dimension for width. For example, a room measuring 12 feet × 15 feet requires those two inputs. The calculator multiplies length × width to determine square footage: 12 × 15 = 180 sq ft. For accuracy, measure at floor level for rooms (walls may not be perfectly vertical). For outdoor spaces, measure at ground level. Add any alcoves, closets, or attached sections separately and sum the results.
For circular areas, measure the diameter (distance across the circle at the widest point) or radius (center to edge). For a round patio, measure across the center: if diameter is 20 feet, radius is 10 feet. The calculator uses the formula π × radius² to calculate area. A 20-foot diameter circle has 10-foot radius: 3.14159 × 10² = 314.16 sq ft. For triangular areas, measure the base (bottom edge) and height (perpendicular distance from base to peak). The calculator uses formula (base × height) ÷ 2.
Review results showing square footage, square meters (for international projects or materials sold in metric), and acres (for large land areas). The calculator also shows square yards for carpet purchases (carpet is sold by the square yard, where 9 sq ft = 1 sq yard). For project planning, the results help estimate materials: flooring, paint, sod, mulch, or concrete. Many construction materials specify coverage rates per square foot, so accurate square footage calculation is essential. Save or print your results for reference when ordering materials or getting contractor quotes.
Understanding Square Footage Calculations
Square footage measures two-dimensional area—the amount of surface within defined boundaries. Understanding square footage is fundamental for any construction, landscaping, or real estate project. One square foot equals a 12-inch by 12-inch square (144 square inches). To visualize: a standard floor tile is approximately 1 square foot. Room size directly translates to comfort and functionality: 100 sq ft is a small bedroom, 150 sq ft is comfortable, 200+ sq ft is spacious. Real estate pricing uses price per square foot as the primary metric—a 2,000 sq ft home at $200 per sq ft costs $400,000.
Converting between square units is necessary for different applications. Square feet to square meters: multiply by 0.092903 (common for international materials or specifications). Square feet to square yards: divide by 9 (carpet is sold by the square yard). Square feet to acres: divide by 43,560 (land measurement). Example conversions: 1,000 sq ft = 92.9 sq m = 111.1 sq yards = 0.023 acres. Conversely, one acre = 43,560 sq ft, helpful when calculating materials for large land areas like sod installation or acreage preparation.
Irregular room shapes require breaking complex areas into simple geometric shapes. L-shaped rooms divide into two rectangles. Measure each rectangle separately and sum: main section 12×15 (180 sq ft) + extension 6×8 (48 sq ft) = 228 total sq ft. Rooms with angled walls or bay windows require approximation: measure the approximate rectangular area and add/subtract triangular sections. For complex architectural features, measure in 2-3 foot sections and sum. Accuracy within 5% is sufficient for most material estimates—precise measurements down to the inch are unnecessary given typical 10% waste factors.
Ceiling height does not affect square footage but dramatically affects volume and related costs. Square footage measures floor area only—a 200 sq ft room with 8-foot ceilings has the same square footage as one with 12-foot ceilings. However, cubic footage (volume) differs: 200 × 8 = 1,600 cubic feet versus 200 × 12 = 2,400 cubic feet. This matters for HVAC sizing, paint quantity, and material costs. Higher ceilings require more paint, more heating/cooling, and more drywall. When planning projects, note ceiling height separately from square footage.
Gross square footage versus livable square footage affects real estate values and material needs. Gross square footage includes all enclosed space: interior rooms, hallways, closets, and walls. Livable (or heated) square footage excludes unfinished areas: garages, unfinished basements, attics, and porches. A 2,500 gross sq ft home might have 2,000 livable sq ft if it includes a 500 sq ft garage. For construction estimates, use gross sq ft for exterior materials (roofing, siding), livable sq ft for interior materials (flooring, paint). Real estate appraisals use livable sq ft, but some builders advertise gross sq ft (appears larger). Always clarify which measurement is being used.
Formula & Calculations
Rectangle area formula: Length × Width = Square Feet. This is the most common calculation. For a room 14 feet long and 11 feet wide: 14 × 11 = 154 square feet. Always use the same units—if measuring in feet and inches, convert everything to feet first. For example, 14 feet 6 inches = 14.5 feet. Calculation: 14.5 × 11 = 159.5 sq ft. Round to 160 sq ft for material ordering. For multiple rectangular areas, calculate each separately and sum: room 1 (154 sq ft) + room 2 (180 sq ft) + hallway (45 sq ft) = 379 total sq ft.
Circle area formula: π × radius² = Square Feet. Radius is half the diameter. For a circular patio with 16-foot diameter: radius = 8 feet. Area = 3.14159 × 8² = 3.14159 × 64 = 201.06 sq ft. Round to 201 sq ft. If you only know circumference (distance around the circle), calculate radius first: radius = circumference ÷ (2 × π). For a 50-foot circumference: radius = 50 ÷ 6.28318 = 7.96 feet. Area = 3.14159 × 7.96² = 199 sq ft. Circular areas are common for outdoor features: round patios, above-ground pools, gazebo floors.
Triangle area formula: (Base × Height) ÷ 2 = Square Feet. Base is any one side, height is perpendicular distance from that side to the opposite vertex. For a triangular yard section with 20-foot base and 12-foot height: (20 × 12) ÷ 2 = 240 ÷ 2 = 120 sq ft. For right triangles (one 90-degree corner), the two perpendicular sides are base and height. For gable ends (triangular wall above rectangular wall), measure base (width of house) and height (peak to eave): 30-foot wide house with 8-foot gable height = (30 × 8) ÷ 2 = 120 sq ft per gable end.
Complex shapes require dividing into simple shapes and summing. For an L-shaped room: divide into two rectangles. Main section 15×18 = 270 sq ft, extension 8×10 = 80 sq ft, total 350 sq ft. For rooms with alcoves or bump-outs: measure main rectangle, then add alcove area. For rounded corners or bay windows: approximate as rectangle (slight overestimate acceptable). For very irregular shapes: use graph paper with 1-foot squares, draw the shape to scale, and count squares (time-consuming but accurate). Professional estimators use laser measuring tools ($100-500) with area calculation functions that handle complex shapes automatically. For DIY projects, rectangular approximation with 10-15% waste factor provides adequate accuracy.
Key Factors to Consider
Measurement precision affects material ordering and costs. Measuring to the nearest inch is sufficient for most projects—precision to 1/8 inch is unnecessary. However, consistent measurement technique matters: always measure at the same height (floor level for rooms), use the same tape measure (different tapes vary slightly), and double-check critical dimensions. A 2-inch measurement error on a 12×15 room (should be 12×15.17) changes square footage from 180 to 182 sq ft—negligible. But a 12-inch error (measuring 12×14 instead of 12×15) reduces square footage from 180 to 168 sq ft, causing material shortage. Always measure twice, verify unusual dimensions, and add 10% waste factor as insurance against measurement errors.
Doors, windows, and built-ins affect usable square footage differently for different projects. For flooring, subtract doors (no flooring under hinged door) but not windows. For paint, subtract both doors and windows. For HVAC sizing, use total floor area including under doors/windows. A 12×15 bedroom with one door (20 sq ft) and one window (15 sq ft): flooring area = 180 - 20 = 160 sq ft. Paint area (walls): calculate wall area (2×12×8 + 2×15×8 = 432 sq ft) minus door and window = 432 - 35 = 397 sq ft. Be consistent with how you handle these features based on project type.
Irregular features like angled walls, rounded corners, and bay windows require approximation strategies. For slight irregularities: ignore them and use rectangular measurement—10% waste factor covers small variations. For significant features: approximate as simpler shapes. A bay window projecting 3 feet from a 5-foot wide wall section: add small rectangle 3×5 = 15 sq ft. Angled walls: measure longest dimensions and approximate as rectangle, or use triangle formula if angle is significant. Curved walls: approximate as rectangle or calculate as circle section if curvature is pronounced. For complex architectural features, conservative estimation (measure slightly larger) prevents material shortage.
Multi-story homes require separate calculations per floor. Total square footage is the sum of all floor areas. For a two-story home: main floor 1,200 sq ft + second floor 1,000 sq ft (smaller due to vaulted ceiling below) = 2,200 total sq ft. Include basement only if finished (heated/cooled living space). Exclude garage, unfinished attic, and exterior porches from livable square footage. For material estimates, calculate each floor separately as material needs differ: first floor may have tile while second has carpet. For HVAC sizing, total all conditioned (heated/cooled) square footage including finished basement but excluding garage and attic.
Property boundaries and setbacks affect outdoor square footage calculations. When measuring yard area for landscaping, distinguish between total lot size and usable area. A 10,000 sq ft lot with 2,000 sq ft house footprint and required 10-foot setbacks from property lines may have only 4,000-5,000 sq ft of usable yard space. Driveways, walkways, and utility easements further reduce landscaping area. For sod, mulch, or hardscaping estimates, measure the specific areas to be covered rather than assuming total lot minus house. Sketch your property with dimensions, mark off unbuildable areas, and calculate usable area for accurate material estimates. Tree canopy and slopes also affect usable area—steep slopes (>15%) are difficult to landscape and may require terracing or alternative treatments.
Frequently Asked Questions
1How do I calculate square footage of a room?
Measure the room length and width in feet using a tape measure, then multiply: Length × Width = Square Feet. For a 12×14 room: 12 × 14 = 168 square feet. For L-shaped or irregular rooms, divide into rectangles, calculate each, and sum totals. Measure in feet and inches, converting inches to decimal feet: 12 feet 6 inches = 12.5 feet. Don't subtract for doors/windows when calculating room size for HVAC or general purposes. Do subtract doors for flooring calculations. Round to nearest square foot—precision beyond that is unnecessary. For whole-house square footage, calculate each room separately and sum: bedroom 168 + living room 240 + kitchen 150 = 558 total sq ft.
2How many square feet is a 12x12 room?
A 12×12 room is 144 square feet (12 × 12 = 144). This is a common size for bedrooms, home offices, or small living spaces. In metric: 144 sq ft = 13.4 square meters. For flooring, subtract approximately 10 sq ft for the door = 134 sq ft of flooring needed. Add 10% waste factor: 134 × 1.10 = 147 sq ft, typically purchase 150 sq ft. For paint, calculate wall area: 2(12+12) × 8-foot ceiling = 48 × 8 = 384 sq ft of walls minus door and windows (approximately 35 sq ft) = 349 sq ft to paint. One gallon of paint covers 350-400 sq ft, so one gallon covers this room for one coat (two coats = 2 gallons).
3How many square feet is an acre?
One acre equals 43,560 square feet. This is equivalent to a square approximately 208.7 feet on each side, though acres can be any shape. Common acre comparisons: 0.25 acre = 10,890 sq ft (common suburban lot), 0.5 acre = 21,780 sq ft, 1 acre = 43,560 sq ft (about 90% of a football field), 5 acres = 217,800 sq ft. To convert square feet to acres: divide sq ft by 43,560. Example: 15,000 sq ft lot = 15,000 ÷ 43,560 = 0.344 acres. To convert acres to square feet: multiply acres by 43,560. Example: 2.5 acres = 2.5 × 43,560 = 108,900 square feet. Useful for land calculations like sod installation, seeding, or acreage preparation.
4Is square footage measured inside or outside walls?
For interior living space, square footage is measured from inside face of exterior walls to inside face of opposite exterior walls (wall-to-wall measurement). This is the usable floor area. Don't subtract for interior wall thickness—measure the entire room including space occupied by interior walls. For real estate and appraisals, measure inside the exterior walls but include all interior space. For whole-house square footage, sum all interior rooms measured wall-to-wall. Gross square footage (sometimes used in construction) measures from outside of exterior walls, including wall thickness—this is 2-5% larger than interior measurement. For material estimates (flooring, paint), always use interior wall-to-wall measurements. Exterior measurements are used only for foundation, framing, and siding calculations.
5How do you measure square footage for flooring?
Measure room length and width at floor level, multiply to get square feet, then subtract door area (where hinged door swings—no flooring needed). Add 10% waste for cuts and mistakes. Example: 14×16 room = 224 sq ft. Subtract door area (typically 20 sq ft for standard door) = 204 sq ft. Add 10% waste: 204 × 1.10 = 224 sq ft of flooring to purchase. For multiple rooms: calculate each separately and sum totals. For L-shaped rooms: divide into rectangles, calculate each, and sum. Don't subtract for closets—they need flooring too. Add transition strips at doorways ($15-30 each). For tile, add 15% waste due to cutting. For diagonal installation, add 15-20% waste. Always round up when ordering—partial boxes aren't sold.
6What is the difference between square feet and square yards?
Square yards and square feet both measure area but use different units. One square yard equals 9 square feet (3 feet × 3 feet = 9 sq ft). To convert square feet to square yards: divide by 9. Example: 225 sq ft = 225 ÷ 9 = 25 square yards. To convert square yards to square feet: multiply by 9. Example: 30 sq yards = 30 × 9 = 270 sq ft. Carpet is sold by the square yard, while most other flooring (hardwood, laminate, tile) is sold by the square foot. When shopping for carpet, convert your square footage to square yards for pricing: 180 sq ft room = 20 square yards. At $25 per square yard, carpet costs $500 plus pad and installation.
7How do I calculate square footage of a house?
Calculate square footage for each room individually, then sum all rooms including hallways, closets, and bathrooms. Measure length and width of each room, multiply for square footage, and add together. Example: bedroom 1 (144 sq ft) + bedroom 2 (168 sq ft) + bathroom (50 sq ft) + living room (240 sq ft) + kitchen (150 sq ft) + hallways (60 sq ft) = 812 total sq ft. Include all interior conditioned (heated/cooled) space. Exclude garage, unfinished basement, attic, and exterior porches from livable square footage. Two-story homes: calculate each floor separately and sum. For real estate listings, professional appraisers use laser measuring tools and calculate from inside exterior walls. Accuracy within 2-3% is acceptable. For material estimates, round to nearest 10-50 square feet and add 10% waste factor.