Bottom line: Roofing material is sold by the square (100 sq. ft. of roof surface), not by the piece, and getting that number wrong is the single biggest reason a Cedar City or Southern Utah job stalls mid-install waiting on a second order. Measure the roof plane, add waste for cuts and pitch, then order metal panels, shingle bundles, or siding by that total — not by guesswork.
How Do You Measure a Roof for Material Ordering?
Start with the footprint of each roof plane (length times width in feet), then convert to squares by dividing by 100. A simple gable roof might take ten minutes to measure; a roof with multiple dormers, valleys, or hips takes longer and benefits from breaking it into smaller rectangles and triangles first. Steeper pitches and cut-up roof lines always need more material than the flat footprint suggests, which is where the next step matters.
What Waste Factor Should You Add?
Waste factor covers the material lost to cuts, overlaps, and fitting around penetrations like chimneys, vents, and skylights. As a general guide:
| Roof complexity | Typical waste factor |
|---|---|
| Simple gable, few penetrations | 5-10% |
| Hip roof or moderate valleys | 10-15% |
| Complex roof, many valleys/dormers | 15-20%+ |
These are typical ranges contractors work from, not a guarantee for every roof — a site-specific walkthrough is still the only way to pin down an exact number. Steeper pitches also increase the actual surface area relative to the footprint, so a steep roof needs its own pitch multiplier before waste is even added.
Metal Panels vs. Shingle Bundles: Why the Math Is Different
Asphalt shingles are sold by the bundle, with bundles-per-square varying by product, so you're matching bundle count to your square total. Metal roofing is different — panels run in fixed widths and custom-cut lengths, so you're ordering by panel count and length rather than rounding up to a bundle. That also means metal orders need a firmer measurement up front, since a short panel can't be patched the way a shingle course can. If you're comparing the two for an upcoming project, our guide to choosing roofing materials for Southern Utah walks through how pitch, budget, and building type affect that choice.
What About Siding and Underlayment Quantities?
Siding is estimated the same basic way — wall area in square feet, minus windows and doors, plus a waste factor for corners and cuts. Underlayment is measured by roof square footage too, but rolls typically cover less area than the roofing material itself once overlap is factored in, so don't assume a 1:1 match between your shingle or panel order and your underlayment order.
Should You Order a Little Extra?
Yes, within reason. A small buffer on top of your waste-factor total covers minor miscuts or a damaged piece discovered during install, without sitting on a large surplus you have to store or return. For current per-unit pricing on shingles, metal panels, and siding so you can turn your square count into an actual order total, see our pricing page. If you want current cost ranges for a full Southern Utah roofing project rather than just materials, our 2026 roofing materials cost guide breaks that down further.
How We Help With the Final Order
Bringing us your measurements — even rough ones — lets our team cross-check quantities before the order is cut, which is a faster way to catch a shortfall than finding out mid-install. Stop by our Cedar City location at 3185 UT-56 with your measurements, or see what we stock locally on our Cedar City roofing products page.