How do I calculate roofing materials for my roof?

Enter roof footprint length and width, select the pitch, and choose shingle or metal. The calculator adjusts for pitch to get actual roof area, then computes squares, asphalt shingle bundles (or metal panels), underlayment rolls, and drip edge length.

How many bundles of shingles per roofing square?

A roofing square is 100 square feet and typically needs three bundles of standard asphalt shingles. The calculator takes your roof dimensions, accounts for pitch, and outputs both squares and the total number of bundles you need.

How does roof pitch affect material estimates?

Pitch is rise over run (a 4/12 pitch means 4 inches of rise per 12 inches of run). A steeper pitch creates more actual roof area than the footprint, so the calculator factors in pitch to avoid under-ordering materials.

Roofing

Roofing Material Calculator

Estimate roofing bundles, squares, underlayment rolls, and drip edge for asphalt shingle or metal panel roofs.

Use this free roofing calculator to turn roof measurements into practical material estimates before you buy shingles, underlayment, drip edge, or accessories. It’s built for DIY planning and roofer takeoffs, with simple roofing math behind every result: actual roof area, roofing squares, bundle estimates, waste allowance, and linear edge measurements.

How it works

Start with the roof footprint area in square feet, then apply a pitch multiplier to estimate the actual sloped roof area: footprint area × pitch multiplier = roof area. Roofing squares are calculated as roof area ÷ 100 sq ft, since 1 roofing square covers 100 sq ft. For architectural shingles, estimate bundles as roofing squares × about 3 bundles per square. Add waste based on roof complexity: simple roofs can stay lean, while hips, valleys, dormers, and cut-up sections often need 10% to 15% extra. Underlayment is estimated by dividing roof area by the coverage of the roll you plan to use. Drip edge is measured in linear feet along eaves and rakes.

Worked examples

Simple shed roof If the actual roof area is 100 sq ft, the roof equals 100 ÷ 100 = 1 roofing square. Architectural shingles would be about 1 × 3 = 3 bundles before waste. With 10% waste, plan for 100 × 1.10 = 110 sq ft of coverage.
Small roof section with architectural shingles If the roof area is 300 sq ft, the roof equals 300 ÷ 100 = 3 roofing squares. Architectural shingles would be about 3 × 3 = 9 bundles before waste. With 15% waste for hips or valleys, plan for 300 × 1.15 = 345 sq ft of coverage.
Cut-up roof with valleys If the roof area is 1,000 sq ft, the roof equals 1,000 ÷ 100 = 10 roofing squares. Architectural shingles would be about 10 × 3 = 30 bundles before waste. With 15% waste, plan for 1,000 × 1.15 = 1,150 sq ft of coverage.

FAQ

What is a roofing square?

A roofing square is a standard roofing unit equal to 100 sq ft of roof area. To find squares, divide the actual roof area by 100.

Why does roof pitch matter?

Pitch changes the real surface area of the roof. A steep roof has more surface area than the flat footprint below it, so the calculator uses a pitch multiplier to convert footprint area into actual roof area.

How many bundles of shingles are in a square?

For architectural shingles, a common planning estimate is about 3 bundles per roofing square. Always check the shingle manufacturer’s coverage before ordering.

How much waste should I add?

For roofs with hips, valleys, dormers, or lots of cuts, add 10% to 15% waste. Waste helps cover trimming, starter runs, overlaps, mistakes, and matching shingle courses cleanly.