Completed exterior siding project used for siding measurement planning

Start with wall area

Break the home into simple rectangles and triangles. Measure each wall width and height, then multiply to estimate square footage. For gables, measure the base and height, multiply them, then divide by two.

Subtract openings carefully

Large windows, doors, and garage doors reduce siding coverage. Small openings and complex trim details may not reduce the estimate as much as expected because they also create extra cuts and waste.

Understand siding squares

A siding square is 100 square feet. Boxes may cover different amounts depending on product, exposure, profile, and manufacturer. Do not assume every box covers the same area.

For actual ordering, product specs and installer layout matter. A field estimate is still the safest final number.

Why waste factor matters

Waste covers cuts around windows, corners, gables, damaged pieces, starter strips, and layout decisions. Simple walls need less waste than homes with many angles, dormers, and details.