Square Footage Calculator

Calculate the square footage of any area — rooms, floors, walls, yards, and land. Supports rectangles, triangles, circles, and trapezoids. Add multiple areas for total square footage with waste factor.

Dimensions & Shapes

Primary Room / Surface
ft
ft
Cutting & Material Waste Margin10%
0% (Exact)10% (Standard)20%+ (Angled/Diagonal)
Total Net Area
120.00 sq ft
Order 132.0 sq ft
Square Meters11.15 m²
Square Yards13.33 yd²
Acres0.0028 ac
Waste Buffer+12.00 ft²

Contractor Tip: Flooring boxes and drywall sheets are sold in fixed increments (typically 20–25 sq ft per box or 32 sq ft per 4×8 sheet). Always round up your calculated total with waste (132 sq ft) to the nearest whole package.

What Is Square Footage and How Is It Measured?

Square footage is the standard imperial measurement of two-dimensional surface area expressed in square feet (ft² or sq ft). One square foot represents the exact area of a square measuring one foot (12 inches) on each side—equivalent to precisely 144 square inches, 0.1111 square yards, or 0.0929 square meters.

1. Geometric Area Formulas (by Shape)
Rectangle / SquareArea = Length (ft) × Width (ft)
Triangle
Area =
Base × Height2
CircleArea = π × Radius² (π ≈ 3.14159)
Trapezoid
Area =
(Side a + Side b) × Height2
2. Material Ordering & Waste Factor Equation
Total Ordered Sq Ft=Net Square Footage ×
[ 1 +
Waste Factor %100
]
Step-by-Step Calculation Breakdown
Step 1: Room Dimension Inputs (15 ft 6 in × 12 ft 0 in)
Convert inches to decimal feet: 6 inches ÷ 12 = 0.50 ft → Length = 15.50 ft | Width = 12.00 ft
Step 2: Calculate Base Net Square Footage
Net Area=15.50 ft × 12.00 ft=186.00 sq ft
Step 3: Add 10% Flooring Cutting & Waste Factor
Total Ordered=186.00 × (1 + 0.10)=186.00 × 1.10=204.60 sq ft (Order 205 sq ft)

Recommended Waste Factors by Construction Material

Material TypeStandard Waste %Cutting Rationale & Pattern Notes
Hardwood & Engineered Planks5% – 10%Straight plank runs require end cuts at walls. Use 10% for angled rooms.
Ceramic & Porcelain Tile10% – 15%Higher tile breakage, wet saw cuts around plumbing fixtures, and herringbone patterns.
Drywall & Sheetrock (4x8 / 4x12)10% – 12%Window, door, and electrical switch box cutouts.
Interior Wall Paint10%1 gallon covers approx. 350–400 sq ft (1 coat). Factor in porous primer absorption.

Square Footage Unit Conversion Table

From UnitTo UnitExact Conversion Factor
Square Feet (sq ft)Square Meters (m²)Multiply by 0.092903
Square Meters (m²)Square Feet (sq ft)Multiply by 10.7639
Square Feet (sq ft)Square Yards (sq yd)Divide by 9 (0.1111)
Square Feet (sq ft)Acres (ac)Divide by 43,560

Common Room Sizes

Room TypeTypical SizeSquare Footage
Small bedroom10×10 ft100 sq ft
Standard bedroom12×12 ft144 sq ft
Master bedroom14×16 ft224 sq ft
Living room12×18 ft216 sq ft
Kitchen10×12 ft120 sq ft
Bathroom5×8 ft40 sq ft
1-car garage12×20 ft240 sq ft
2-car garage20×24 ft480 sq ft

Sources and References

  • National Institute of Standards and Technology (NIST). (2023). The International System of Units, 9th edition. NIST SP 330.
  • National Association of Home Builders. (2022). Typical Room Dimensions and Square Footage by Home Size. Housing Economics.
  • Residential Construction Standards, International Residential Code (IRC). (2021). ICC Digital Codes.

Frequently Asked Questions

How do I calculate square footage?
For a rectangle or square, multiply length × width. For example, a room that is 12 feet long and 10 feet wide is 120 square feet (12 × 10 = 120). If your measurements include inches, convert them to decimal feet first: divide inches by 12 and add to the feet measurement. So 12 feet 6 inches = 12.5 feet. For non-rectangular shapes, our calculator provides formulas for triangles, circles, and trapezoids.
How do I convert square feet to square meters?
Multiply square feet by 0.0929 to get square meters. For example, 500 sq ft × 0.0929 = 46.45 sq m. To convert square meters to square feet, multiply by 10.764. Our calculator provides automatic conversions between all common area units including square feet, square meters, square yards, and acres.
How do I calculate square footage for an irregularly shaped room?
Break the irregular shape into smaller regular shapes (rectangles, triangles, etc.). Calculate the area of each shape separately, then add them together. For example, an L-shaped room can be divided into two rectangles. A room with a bay window can be calculated as a rectangle plus a triangle or trapezoid. Use our multi-area feature to add multiple shapes and get the total automatically.
How much flooring do I need?
Calculate the total square footage of the area, then add 5–10% for waste (cutting, mistakes, and future repairs). For tile, add 10–15% because tiles must be cut at walls and transitions. For hardwood, add 5–10%. For carpet, rolls come in standard widths (12 or 15 feet), so calculate based on roll layout to minimize seams. Our calculator includes a waste factor to help you order the right amount.
What is the difference between square feet and linear feet?
Square feet measures area (two dimensions — length × width), while linear feet measures only length (one dimension). If you buy 100 linear feet of fencing, that's the total length. If you buy 100 square feet of flooring, that covers a 10×10 foot area. Materials like crown molding, baseboards, and gutters are sold by linear foot, while flooring, paint coverage, and roofing are sold by square foot.
How do I calculate wall square footage for painting?
Multiply the wall length × wall height to get the total wall area. For a room, add up all four walls, then subtract the area of doors (approximately 21 sq ft each for standard doors) and windows (approximately 15 sq ft each for standard windows). One gallon of paint typically covers 350–400 square feet with one coat. For two coats, double the area or halve the coverage per gallon.

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