Square Footage Calculator — Area & Cost
Calculate area for flooring, painting, roofing. Supports rectangles, circles, triangles. Add waste and cost per sq ft.
Why This Construction Metric Matters
Why: Accurate square footage prevents over- or under-ordering of flooring, paint, roofing.
How: Rectangle: L×W. Circle: πr². Triangle: ½×base×height. Add 10–15% waste.
- ●Rectangle L×W; circle πr²; triangle ½bh
- ●Add 10–15% waste for flooring
- ●Wall area = 2×(L+W)×H
- ●1 sq ft = 0.0929 m²
📋 Quick Examples — Click to Load
Planning estimates only. Verify with a licensed engineer or contractor before construction.
📐 Construction Industry Facts
Rectangle area = L × W
— Geometry
Circle area = π × r²
— Geometry
Triangle area = ½ × base × height
— Geometry
Square footage is area in sq ft. Rectangle: L×W. Circle: πr². Triangle: ½×base×height. Add 10–15% waste for flooring. 1 sq ft = 0.0929 m² = 1/9 sq yd.
Sources: ICC, NAHB, DOE Building Energy.
Key Takeaways
- • Rectangle: Area = Length × Width
- • Circle: Area = π × radius²
- • Triangle: Area = ½ × Base × Height
- • Add 10–15% waste for materials
Did You Know?
How Does Square Footage Work?
Rectangle
Multiply length by width. Example: 12 ft × 10 ft = 120 sq ft.
Circle
Area = π × r². Radius = diameter ÷ 2. Example: 10 ft diameter → 78.5 sq ft.
Triangle
Area = ½ × base × height. Use perpendicular height.
Expert Tips
Common Room Sizes
| Room | Typical (sq ft) |
|---|---|
| Master Bedroom | 200–400 |
| Standard Bedroom | 120–200 |
| Living Room | 200–400 |
| Kitchen | 100–250 |
Frequently Asked Questions
What is square footage?
Square footage is the area measured in square feet (sq ft). One sq ft equals a 12" × 12" square. It's the standard unit for floor area, wall area, and land in the US.
How do I calculate square footage for a rectangle?
Multiply length by width: Area = L × W. Example: 14 ft × 12 ft = 168 sq ft. Measure at floor level, wall to wall.
How much waste should I add for flooring?
Add 10–15% waste for flooring, tile, and roofing. Simple rectangles need ~10%; L-shapes, patterns, or diagonal installs need 15–20%.
What is the formula for circular area?
Circle area = π × r². If you have diameter, divide by 2 for radius. Example: 10 ft diameter → r=5 ft → π×25 ≈ 78.5 sq ft.
How do I calculate wall area for painting?
Wall area = 2 × (Length + Width) × Height. Subtract windows and doors. One gallon typically covers 350–400 sq ft per coat.
What is 1 square foot in other units?
1 sq ft = 144 sq in, 0.0929 sq m, 1/9 sq yd. 1 acre = 43,560 sq ft. Carpet and turf are often sold by square yard.
Key Statistics
Official Data Sources
⚠️ Disclaimer: Estimates only. Verify measurements. Add waste for materials. Consult a professional for complex projects.
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