Siding Calculator: Squares, Square Feet and Cost

How to work it out

Measure each wall's width and height, and enter them as length and width. Add each wall as its own area.
Add each gable end as a triangle: the base is the wall width and the height is from the eaves to the peak.
Add up the doors and windows and enter the total to subtract.
Keep some extra for cuts and overlaps. The calculator starts with 10%.

Quick reference

Item	Value
One square of siding	100 sq ft
Typical front door	About 20 sq ft
Typical window, 3 by 4 ft	12 sq ft

These are common starting points. Your site, climate and supplier may call for something different.

What this leaves out

Trim, corners, J-channel, soffit, house wrap and fasteners are bought separately. Measure trim in linear feet around doors, windows and corners.

Common questions

How many squares of siding do I need?

Add up the wall area, subtract doors and windows, add about 10% for waste, then divide by 100. A house with 1,500 sq ft of wall after openings needs about 16.5 squares.

What is a square of siding?

100 sq ft of wall coverage. Siding is often priced and sold by the square.

How do I measure a gable?

Treat it as a triangle: the base is the width of the wall and the height runs from the bottom of the triangle to the peak. Choose Triangle as the shape and the calculator halves it for you.

Doing this job for a customer? Turn your numbers into a free written estimate on QuoteToPaid.

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