Square Foot Calculator
Calculate square footage for rectangular rooms, circles, and triangles, with waste factor margins, square yard conversions, and total cost estimates.
Calculation Results
The exact geometric surface area in square feet.
Total material square footage required including cutting scrap margin.
Area in square yards (standard unit for carpet rolls, turf, and sod).
Equivalent surface area in metric square meters.
Estimated total cost based on the material required with waste.
How This Calculator Works
Measure and calculate square footage in three simple steps:
- Choose Shape: Select rectangle for standard rooms and walls, circle for round patios, or triangle for gable walls.
- Enter Dimensions: Input lengths in feet (e.g., convert 10 feet 6 inches to 10.5 feet).
- Select Waste Allowance: Include 10% for flooring or drywall to account for perimeter cuts and awkward corners.
- View Trade Conversions: Check square feet, square yards, and metric square meters for ordering.
Formula & Calculations
Square footage calculations determine 2D plane surface area based on Euclidean geometry:
1. Geometric Formulas
- Rectangles:
Area = Length × Width - Circles:
Area = π × (Diameter / 2)² - Triangles:
Area = (Base × Height) / 2
2. Trade Unit Conversions
- Square Yards:
Square Feet / 9(since 1 yard = 3 feet, 1 sq yd = 3 × 3 = 9 sq ft). Essential for carpet, sod rolls, and geotextile fabrics. - Square Meters:
Square Feet × 0.092903(1 m² = 10.7639 sq ft). - Acres: 1 Acre = 43,560 square feet.
Step-by-Step Calculation Examples
Finished Basement Living Room (20ft x 15ft)
Calculating flooring square footage and carpet yardage with 10% waste at $4.50/sq ft.
- shape: rectangle
- length: 20
- width: 15
- waste: 10
- cost_per_sqft: 4.5
- net_area_sqft: 300.0 sq ft
- total_area_with_waste: 330.0 sq ft
- area_sq_yd: 36.67 sq yd
- area_sq_m: 30.66 m²
- estimated_project_cost: $1485.00
Frequently Asked Questions
How do you calculate square footage from inches?
Measure your length and width in inches, multiply them together to get square inches, and divide by 144 (since 12" x 12" = 144 sq in). For example, a 120" by 180" room equals 21,600 sq in / 144 = 150 square feet.
How do you calculate square footage of an L-shaped room?
Divide the L-shape into two separate rectangles (Section A and Section B). Measure length and width of each section, calculate their square footages independently (Area A = L1 x W1, Area B = L2 x W2), and add them together.
How many square feet are in a square yard?
There are exactly 9 square feet in 1 square yard. To convert square feet to square yards (used for carpet and sod), divide total square footage by 9.
What is the difference between net square footage and gross square footage?
Net square footage is the exact physical interior usable floor space. Gross square footage includes the thickness of exterior and interior partition framing walls, utility closets, and ductwork chases.
How many square feet are in one acre?
One acre equals exactly 43,560 square feet (an area roughly 208.7 feet by 208.7 feet, or approximately 90% the size of an American football field).
Why do contractors add 10% waste to square footage?
Standard building materials (drywall panels, plywood subflooring, hardwood planks, tile) come in rigid rectangular sizes. Cutting these materials to fit room borders, doorways, and electrical boxes creates unusable scrap off-cuts.