Siding Calculator

How to Calculate Siding for Your Home

Our siding calculator helps you estimate materials for vinyl, fiber cement, wood, and other siding types. Enter your wall dimensions, gable areas, and window/door openings to get accurate estimates.

What is a Square of Siding?

A "square" is an industry-standard measurement equal to 100 square feet of siding coverage. This is how siding is typically sold by manufacturers and contractors.

How Much Extra Siding Should I Order?

We recommend ordering 10-15% extra siding to account for:

• Cuts and waste around windows and doors
• Mistakes during installation
• Damaged pieces that may need replacement
• Complex architectural features

The Siding Formula

This calculator uses the same math contractors use for a first-pass material estimate:

1. Wall area: wall height x total wall length (measure each wall and add the lengths together)
2. Gable area: 0.5 x gable width x gable height for each triangular gable section
3. Net area: gross wall area minus the total area of windows and doors
4. Order quantity: net area plus 10% waste, expressed in squares (1 square = 100 sq ft)

Trim pieces are estimated separately: starter strip runs the full length of all walls plus 10%, and J-channel is estimated from the total window and door area.

Worked Example: Single-Story Ranch

A single-story home with 120 ft of combined wall length, 9 ft walls, one gable 30 ft wide and 5 ft tall, and 150 sq ft of windows and doors:

• Wall area: 9 ft x 120 ft = 1,080 sq ft
• Gable area: 0.5 x 30 ft x 5 ft = 75 sq ft
• Gross area: 1,080 + 75 = 1,155 sq ft; net after openings: 1,155 - 150 = 1,005 sq ft
• With 10% waste: 1,005 x 1.1 = about 1,106 sq ft, or 11.1 squares
• Trim: about 132 ft of starter strip and 59 ft of J-channel

At the 2026 installed range of $4-$13 per sq ft of net wall area, that project lands roughly between $4,000 and $13,100 depending on material, region, and site conditions.

Siding Cost Factors and Common Mistakes

Material choice is the biggest cost driver. Vinyl is usually the least expensive to install, fiber cement costs more in labor because it is heavy and needs special cutting tools, and wood or engineered wood products sit at the top of the range. Cost also varies by region, the condition of the existing walls, and whether old siding needs to be removed and hauled away.

• Waste factor: 10% covers simple rectangular walls; go to 15% with gables, dormers, and lots of openings
• Old siding: tear-off adds cost but lets you inspect the sheathing and install a new water-resistive barrier
• Common mistakes: measuring one wall and multiplying, forgetting gables, and skipping trim pieces (starter strip, J-channel, inside/outside corners) in the order
• Insulation: adding a layer of rigid foam or insulated siding raises material cost but can improve comfort and energy bills

FAQ

How many squares of siding for a 1500 sq ft house?

A typical 1500 sq ft single-story home needs about 15-20 squares of siding, depending on layout and window/door openings.