Siding measurement calculator: squares, boxes, and waste
Enter your home’s footprint, number of stories, gable ends, and openings to estimate total exterior wall area, siding squares, the waste allowance, and the total boxes to order. One siding square covers 100 sq ft of wall.
Calculator
- Wall perimeter160 ft
- Flat wall area2,880 sq ft
- Gable triangles+240 sq ft
- Windows & doors−216 sq ft
- Siding squares29.0
- Waste allowance (15%)+4.4 sq
- Squares to order33.4
- Boxes (≈2 squares each)17
One siding square covers 100 sq ft of wall. This estimate uses an average 9 ft story height and an 18 sq ft deduction per opening. Actual material depends on profile, exposure, corner posts, J-channel, and starter strip. Always confirm with your contractor’s measured take-off before ordering.
How to measure your home for siding
Step 1: Measure the footprint. From the ground, measure the length and width of the house at the foundation. For a rectangular house this is straightforward; for an L-shape, break it into rectangles and add the perimeters.
Step 2: Count the stories. The calculator uses an average finished wall height of 9 ft per story. A 1.5-story home (a story-and-a-half with knee walls) sits between the one- and two-story figures.
Step 3: Count the gable ends. Each gable adds a triangular wall section above the eave line. The calculator estimates each gable at roughly half the wall width by an 8 ft rise. Houses with hip roofs have no gables.
Step 4: Deduct openings and add waste. Subtract about 18 sq ft for each window and door. Then add a waste allowance: ~10% for a simple boxy home, ~15% for an average elevation, and up to 20% for a complex home with many corners, dormers, and trim runs.
Wall area quick-reference table
| Footprint | Stories | Approx. wall area | Siding squares |
|---|---|---|---|
| 30 × 40 ft | 1 story | ~1,260 sq ft | ~13 sq |
| 30 × 40 ft | 2 story | ~2,520 sq ft | ~25 sq |
| 40 × 50 ft | 1 story | ~1,620 sq ft | ~16 sq |
| 40 × 50 ft | 2 story | ~3,240 sq ft | ~32 sq |
| 50 × 60 ft | 2 story | ~3,960 sq ft | ~40 sq |
Directional figures before opening deductions and waste. Wall area = perimeter × 9 ft × stories. A real take-off accounts for gables, soffit, and trim.
Frequently asked questions
- What is a siding square?One siding square equals 100 square feet of wall area. Contractors quote material and labor per square, the same unit used for roofing. A house with 2,000 sq ft of wall is 20 squares.
- How do I measure my exterior wall area?Measure the footprint length and width of the house, double the sum to get the wall perimeter, then multiply by wall height (about 9 ft per story). Add a triangle for each gable end and subtract roughly 18 sq ft for every window and door. The calculator does all of this for you.
- How many boxes of siding do I need?It depends on the profile. Double-4 vinyl siding covers about 2 squares per box, so a 20-square house needs roughly 10 boxes plus waste. Fiber cement lap siding is sold by the piece or by the square. The calculator estimates boxes at 2 squares each and adds a waste allowance.
- Why does siding waste run higher than roofing waste?Every window, door, and corner forces an off-length cut, and the offcuts are often too short to reuse. Plan 10% waste on a simple boxy house, 15% on an average home, and up to 20% on a complex elevation with many corners and dormers.
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