Roofing, Siding & Insulation Calculators

Roofing, siding and insulation are measured by area and priced by the square, the bundle or the R-value. The tools here estimate quantities with a waste allowance. These are also the jobs with the highest risk of falls, so many are better left to experienced contractors.

Which tool answers which question

• Insulation Calculator: Target R-value and insulation type in; depth, bags or board feet out.
• Roofing Shingles Calculator: Footprint and roof pitch in; roof area, squares and shingle bundles out.
• Siding Calculator: Wall and gable area minus openings, siding squares with waste, and vinyl boxes.

Squares, pitch and waste

Roofing is measured in squares of 100 square feet. A steeper roof has more surface than its plan area, so the tool applies a pitch factor, and shingles typically need about three bundles per square plus extra for hips, valleys and waste. Siding uses wall area less openings plus an allowance for cuts.

Insulation and safety

Recommended insulation R-values depend on your climate zone and where in the house the insulation goes, so check the guidance for your area. Work on a roof calls for fall protection and good conditions, and removing old roofing or siding may uncover asbestos in older homes.

Common mistakes

• Measuring the plan area only. Pitch adds surface.
• Skipping the waste allowance. Hips and valleys use extra.
• Working on a wet or icy roof. Falls are the main danger.
• Ignoring local code. Check wind, fire and ventilation rules.