5 calculators
Roofing & Exterior Calculators
Roofing and exterior calculators: roof area and squares, roof pitch, shingle bundles, siding and gutters. Plan materials and cost before you order.
Which roofing or exterior calculator do you need?
- A full roof estimate: the roofing calculator gives roof area, squares, bundles, underlayment, drip edge and ridge cap.
- Just the shingles: the shingle calculator turns a known roof area into bundles.
- The slope of a roof: the roof pitch calculator converts rise and run to pitch, angle and pitch factor.
- Walls: the siding calculator handles walls, gables and openings in squares and boxes.
- Gutters: the gutter calculator counts sections, hangers, downspouts and fittings.
Squares, pitch and roof area
Roofing and siding are both sold by the square: 100 square feet. Walls are easy to measure from the ground, but a roof is larger than the house footprint because it slopes. Multiply the footprint (including overhangs) by the pitch factor to get the true roof area: about 1.05 for a 4:12 roof, 1.12 for 6:12 and 1.41 for a 12:12 roof. Then add waste for cuts: 10% on a simple gable roof, 15% on hips and valleys.
Example: estimating a re-roof
A house measures 40 × 30 ft including the overhangs, so its footprint is 1,200 ft². With a 6:12 pitch the roof area is 1,200 × 1.118 ≈ 1,342 ft², or about 13.4 squares. Adding 10% for a simple gable roof gives 14.8 squares, so you would order 15 squares: 45 bundles of three-tab or architectural shingles, plus underlayment, drip edge for the eaves and rakes, starter strip and ridge cap. The roofing calculator does all of this from the footprint and pitch.
Exterior materials checklist
- Roof: shingles, underlayment, ice and water shield at eaves and valleys in cold climates, drip edge, starter strip, ridge cap, roofing nails and vents.
- Siding: panels by the square, starter strip, J-channel around windows and doors, corner posts, soffit and fascia.
- Gutters: sections, hangers about every 2 ft, end caps, corners, outlets and downspouts with elbows, roughly one downspout per 30–40 ft of gutter.
Working safely
Measuring a roof from the ground or the attic is safer than walking it. If you do go up, use fall protection on steep roofs, never work on wet or icy surfaces, and keep ladders secured. For large or steep roofs, many homeowners measure for budgeting and leave the installation to a licensed roofer.
What these calculators do not do
They estimate materials and cost. They do not design roof structures, ventilation or drainage, size gutters for rainfall, or confirm code compliance. Manufacturer instructions and your local building department set those requirements.