Estimating Installing Vinyl Siding

These formulas apply for both horizontal and vertical installations.

NOTE: When estimating for a large project, you may want to add a waste allowance of 10 percent to the totals for siding, soffit and accessories.

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Rectangular wall surfaces

Measure height (excluding gables). Measure width

(including doors and windows).

_____________ x _____________ = _____________

(height) (width) (surface area)

Repeat for remaining walls.


Triangular gable end surfaces

Measure height at center (add 1' to allow for waste).

Measure width and divide by half.

_____________ x _____________ = _____________

(height) (1/2 width) (surface area)

Repeat for remaining gables.

NOTE: Lower pitch roofs will produce more waste than higher pitch roofs.

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Upper wall of gambrel house

Divide the upper wall of a gambrel house as shown in the

illustration. Then use the following formulas:

1/2 (B + C) x H = ____________

1/2 C x D = ____________

Add these figures to get total area: ____________

Repeat for remaining gambrel surfaces.


Dormer sides

Measure height of dormer (add 1' to allow for waste).

Use the following formula:

_____________ x _____________ = ____________________

(1/2 height) (1/2 width) (surface area, 1 side)

____________________ x 2 = _________________________

(surface area, 1 side) (total dormer surface area)

Repeat for all dormers.



Measure width of eave to be covered. Measure length of eave.

_____________ x _____________ = _____________

(width) (length) (surface area)

Repeat for remaining eaves.


Porch Ceiling

Measure length of porch area to be covered and width

of porch.

_____________ x _____________ = _____________

(length) (width) (surface area)

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