Siding Calculator
Free Siding Calculator for construction. Enter project dimensions to estimate materials, costs, and requirements.
Formula
Squares = (Wall Area + Gables - Openings) × Waste / 100
Calculate total wall and gable area, subtract window and door openings, add waste factor, then divide by 100 to get squares (industry standard unit).
Worked Examples
Example 1: Single Story Ranch
Problem: 40×30 ft house, 10 ft walls, 2 gables with 3-ft rise, 8 windows, 2 doors, vinyl siding.
Solution: Wall area:\n2(40 × 10) + 2(30 × 10) = 800 + 600 = 1,400 sq ft\n\nGable area:\n2 gables × (30 × 3 / 2) = 2 × 45 = 90 sq ft\n\nSubtract openings:\n8 windows × 15 = 120 sq ft\n2 doors × 21 = 42 sq ft\nTotal: 162 sq ft\n\nNet area: 1,400 + 90 - 162 = 1,328 sq ft\n\nWith 10% waste:\n1,328 × 1.10 = 1,461 sq ft\n\nSquares: 1,461 ÷ 100 = 14.6 → 15 squares
Result: 15 squares vinyl siding | ~$5,250
Example 2: Two Story Colonial
Problem: 50×30 ft two-story, 20 ft total wall height, 4 gables, 16 windows, 3 doors.
Solution: Wall area:\n2(50 × 20) + 2(30 × 20) = 2,000 + 1,200 = 3,200 sq ft\n\nGables (4 ft rise each):\n4 × (30 × 4 / 2) = 4 × 60 = 240 sq ft\n\nSubtract:\n16 windows × 15 = 240 sq ft\n3 doors × 21 = 63 sq ft\nTotal: 303 sq ft\n\nNet: 3,200 + 240 - 303 = 3,137 sq ft\n\nWith 15% waste (complex):\n3,137 × 1.15 = 3,608 sq ft\n\nSquares: 36.08 → 36 squares
Result: 36 squares | $12,600 vinyl | $28,800 fiber cement
Example 3: Small Cottage
Problem: 24×20 ft cottage, 8 ft walls, 2 small gables, 4 windows, 1 door.
Solution: Walls:\n2(24 × 8) + 2(20 × 8) = 384 + 320 = 704 sq ft\n\nGables (2.5 ft rise):\n2 × (20 × 2.5 / 2) = 50 sq ft\n\nSubtract:\n4 windows × 15 = 60 sq ft\n1 door × 21 = 21 sq ft\n\nNet: 704 + 50 - 81 = 673 sq ft\n\nWith 10% waste:\n673 × 1.10 = 740 sq ft\n\nSquares: 7.4 → 8 squares
Result: 8 squares siding | $2,800
Frequently Asked Questions
How do I calculate siding for my house?
Step-by-step process: 1) Calculate wall area: 2(Length × Height) + 2(Width × Height). 2) Add gable areas: Each gable = 0.5 × base width × vertical rise. 3) Subtract openings: ~15 sq ft per standard window, 21 sq ft per standard door, 70-140 sq ft per garage door. 4) Add 10-15% waste for cuts, mistakes, and future repairs. 5) Divide by 100 to get 'squares' (industry unit). Example: 40×30 ft house, 10-ft walls, 2 gables (3-ft rise each): Walls = 2(400) + 2(300) = 1,400 sq ft. Gables = 2 × (30 × 3 / 2) = 90 sq ft. Subtract 8 windows (120) + 2 doors (42) = 162 sq ft. Net = 1,328 × 1.10 waste = 1,461 sq ft = 14.6 → 15 squares.
What is a square of siding?
A 'square' is a measurement unit in roofing and siding industries = 100 square feet of coverage. Siding priced and sold by the square. Price per square varies by material: Vinyl: $300-500 per square. Fiber cement: $400-800 per square. Wood: $600-1,200 per square. Metal: $400-700 per square. Brick/stone veneer: $1,500-3,000 per square. Calculate: Total wall area ÷ 100 = squares needed. Example: 1,500 sq ft house needs ~18-22 squares (varies with openings and waste). Always add minimum 10% waste - siding cuts, mistakes, matching future repairs. Buy 1-2 extra squares for future repairs (colors can be discontinued, batches vary).
What are the different types of house siding?
Vinyl siding: $3-8/sq ft, low maintenance, 20-30 year life, wide color selection, can crack/fade, most popular (30% market). Fiber cement (Hardie board): $5-12/sq ft, extremely durable, 50+ years, paintable, fire-resistant, heavy (professional install), gaining market share. Wood (cedar/redwood): $6-15/sq ft, beautiful natural look, requires maintenance (paint/stain every 3-7 years), 20-40 year life. Engineered wood: $4-9/sq ft, similar to wood but more stable, needs painting. Metal/Aluminum: $4-10/sq ft, 40+ years, fire-resistant, can dent, industrial look unless textured. Brick/Stone veneer: $15-30/sq ft, permanent, high-end look, expensive. Stucco: $6-9/sq ft, regional (Southwest), textured, needs periodic maintenance. Best choice depends on: Climate (vinyl brittle in extreme cold, wood rots in humid climates), budget, maintenance willingness, architectural style, HOA restrictions.
Should I subtract windows and doors from siding calculations?
Yes - always subtract window and door openings from total wall area. Standard window: 15-20 sq ft (3×5 or 4×5 ft typical). Bay window: 30-50 sq ft. Entry door: 21 sq ft (3×7 ft). French doors: 40-60 sq ft. Garage door: Single 70-90 sq ft, Double 140-160 sq ft. However: Some contractors don't subtract very small windows (<10 sq ft) to account for cutting waste around openings. Add extra siding around each opening: J-channel or trim needed, adds material. Complex windows (many mullions, odd shapes): May need 20-25% waste factor due to cutting complexity. For estimating: Subtract major openings, add appropriate waste percentage to account for trim cuts.
How much trim do I need for siding?
Measure all locations needing trim: Corner boards: Building height × 4 corners (outside corners) = linear feet. Inside corners: J-channel or boards. Window trim: Perimeter of each window (typically 14-16 ft per window). Door trim: Perimeter of each door (typically 18-20 ft per door). Starter strip: Bottom of all walls (perimeter of house). J-channel: Around all windows/doors plus roof lines. Fascia: Along roof edges. Frieze board: Top of walls at roof line. Formula: Sum all measurements × 1.10 for waste. Trim typically adds $3-8 per linear ft to siding cost. Pre-finished trim (color-matched to siding) worth premium for easier installation and better appearance than field-painting.
Can I install siding myself?
Vinyl siding: Most DIY-friendly, snap-lock system, forgiving of minor mistakes. Difficulty: Moderate. Special tools needed (~$100-200): J-channel cutter, snap lock punch, zip tool, utility knife, tin snips, level. Skills: Cutting, measuring, following instructions. Time: 1,500 sq ft house = 1-2 weeks for first-timer, 3-5 days experienced. Fiber cement: Difficult DIY - very heavy (requires 2 people per board), special saw blade needed (carbide), silica dust control critical (respirator), precise cuts required. Wood siding: Moderate-difficult, requires carpentry skills, painting/staining needed. Most DIYers: Vinyl siding saves 40-60% on labor. Take time, watch videos, work with helper. Fiber cement/wood: Consider professional - quality installation critical for longevity.