How to Use the Siding Quantity Calculator

Use the Builzee siding quantity calculator to estimate how much siding material you need for rectangular walls and triangular gables.

Start by entering each wall or gable as a separate section. For repeated walls with the same dimensions, use the Qty field instead of entering the same section multiple times.

For each section, enter:

• wall or gable dimensions
• quantity
• optional opening area to deduct

Then choose the siding material, waste allowance and optional package coverage.

The calculator combines all sections and estimates total siding area, siding squares and package quantity when product coverage is provided.

Measuring Rectangular Walls

For a rectangular wall, measure the full width and height.

The calculator uses:

Wall Width × Wall Height

For example, a wall measuring 30 feet wide by 10 feet high has:

30 × 10 = 300 square feet

If several identical walls use the same dimensions, increase the Qty rather than entering each one separately.

Measuring Triangular Gables

For a triangular gable, measure the base width and vertical height from the base of the triangle to the peak.

The calculator uses:

Base Width × Gable Height ÷ 2

For example, a gable measuring 24 feet wide and 8 feet high contains:

24 × 8 ÷ 2 = 96 square feet

Enter rectangular wall areas and triangular gables as separate siding sections.

Should You Subtract Windows and Doors?

The calculator includes an optional Openings to Deduct field for windows, doors and other areas that will not receive siding.

Large openings are usually worth deducting because they can significantly affect the material estimate.

For example, a 6-foot-wide by 7-foot-high door occupies:

42 square feet

For small windows or openings, some homeowners may choose to leave the area included to provide additional material for cuts and waste.

The Builzee calculator keeps opening deductions and waste separate so you can clearly see how each affects the final estimate.

What Is a Siding Square?

Siding quantities are often discussed in squares.

One siding square equals:

100 square feet

For example:

750 square feet = 7.5 siding squares

The calculator shows both:

Siding Squares Before Waste

and

Siding Squares Including Waste

The figure including waste is generally the more useful number when planning material quantities.

How Much Waste Should You Add for Siding?

Siding installation normally requires some additional material for cuts, damaged pieces and layout adjustments.

Waste may come from:

• trimming around doors and windows
• corners
• gables
• short wall sections
• starter and termination conditions
• damaged pieces
• unusable offcuts

The calculator uses 10% waste as the standard setting.

Simple walls may require less, while homes with many windows, gables, corners or irregular surfaces may require more.

Use the waste percentage that best reflects the actual project.

Estimating Siding Packages

Siding is sold in cartons, bundles or other package sizes depending on the material and manufacturer.

Use the optional Coverage Per Package field when you know how much area one package covers.

For example, if the project requires:

648 square feet

and each package covers:

80 square feet

the calculation is:

648 ÷ 80 = 8.1 packages

Because you cannot purchase a fraction of a package, the calculator rounds up to:

9 packages

Always use the actual net coverage listed by the siding manufacturer.

Vinyl Siding

Vinyl siding is commonly sold in cartons with a stated coverage area.

Different profiles and manufacturers can have different package quantities, so the calculator does not assume a universal carton size.

Enter the actual Coverage Per Package when it is available.

The same approach can be used for other siding materials when the manufacturer provides a clear package coverage figure.

Fiber Cement, Wood and Other Siding Materials

The calculator can also estimate surface area for:

• fiber cement
• engineered wood
• wood siding
• metal siding
• composite siding
• other siding products

The total square footage and siding-square calculations work the same way.

However, individual plank, panel or piece quantities depend on the specific product dimensions and installation exposure.

Use the calculator’s total siding area as the starting point and follow the manufacturer’s coverage information for final material quantities.

Calculating Multiple Walls and Gables

Most siding projects involve several different wall sections.

Use Add Another Siding Section to enter each area separately.

For example, a house might include:

• two identical side walls
• one front wall with several windows
• one rear wall
• two triangular gables

The Qty field is useful when identical sections repeat.

The calculator combines all entered sections before applying the waste allowance.

Understanding the Section Breakdown

The results include a breakdown for each wall or gable.

This makes it easier to see:

• gross area
• opening deductions
• net siding area
• section quantity

A section breakdown can also help identify measurement mistakes before material is ordered.

If one wall shows an unexpectedly high or low area, recheck the dimensions before relying on the total.

What the Siding Calculator Does Not Include

The calculator is designed to estimate the main siding surface material.

It does not automatically calculate:

• corner posts
• J-channel
• starter strips
• trim boards
• soffit
• fascia
• flashing
• housewrap
• fasteners
• caulk
• labor
• project cost

Those materials depend heavily on the siding system, house layout and manufacturer installation requirements.

Before You Order Siding

Measure each wall and gable carefully before purchasing material.

Also verify:

• window and door dimensions
• siding product coverage
• package quantities
• waste allowance
• manufacturer installation instructions
• trim requirements
• corner conditions
• soffit and fascia requirements

For larger projects, compare the calculator result with the siding supplier’s material takeoff before placing the final order.