Siding Calculator – Guide & Formulas
Calculate the total square footage of vinyl, wood, metal, or fiber cement siding needed, subtracting windows and doors.
Determine how much siding to purchase for your home exterior. Input individual wall segments, deduct windows, doors, and gables, and compare material requirements with waste margins.
Key Takeaway
Use the free Siding Calculator to calculate the total square footage of vinyl, wood, metal, or fiber cement siding needed, subtracting windows and doors. Get instant results with step-by-step explanations.
How to Use the Siding Calculator
- Enter individual wall lengths and heights.
- Input the quantity and dimensions of windows and doors to deduct.
- Set your preferred waste factor and view total square footage and cost estimations.
The Formula
Variable Definitions
- Walls Area: Sum of all solid rectangular wall segments
- Deductions Area: Sum of all window and door cutout areas
Siding a Simple Front Wall
Estimate siding for a 40 ft wide by 10 ft high front wall containing two 3x5 windows and one 3x7 front door, with 10% waste.
- Step 1: Calculate total wall footprint: 40 × 10 = 400 sq ft.
- Step 2: Calculate window deductions: 2 × (3 × 5) = 30 sq ft.
- Step 3: Calculate door deduction: 3 × 7 = 21 sq ft. Total deductions = 51 sq ft.
- Step 4: Calculate net area with waste: (400 - 51) × 1.10 = 383.9 sq ft.
Frequently Asked Questions
How much waste should I calculate for siding?
For standard horizontal vinyl siding, 10% is standard. For diagonal siding, complex shapes, or cedar shakes, use a 15-20% waste margin.
What is a "Square" of siding?
Like roofing, siding materials are often sold in squares, where 1 square equals 100 square feet of coverage.
Does siding require backing or house wrap?
Yes, house wrap (vapor barrier) is typically installed under the siding and usually matches the net wall area without deductions.