Roofing Calculators
Free roofing calculators for gable, hip, shed, gambrel, and flat roofs. Enter your dimensions and pitch to get exact shingle bundles, squares, underlayment rolls, and ridge cap — instantly.
Gable Roof Calculator
A gable roof is the most common roof style in North America — two equal slopes meeting at…
Calculate now →Hip Roof Calculator
A hip roof slopes on all four sides and meets at a central ridge — giving a more…
Calculate now →Shed / Lean-To Roof Calculator
A shed roof (also called a lean-to or mono-pitch roof) has a single slope running in one direction.…
Calculate now →Gambrel (Barn) Roof Calculator
A gambrel roof — often called a barn roof — has two pitches on each side: a shallower…
Calculate now →Flat / Low-Slope Roof Calculator
Flat and low-slope roofs (under 2:12 pitch) use membrane systems — EPDM, TPO, or modified bitumen — instead…
Calculate now →About these roofing calculators
Every calculator on this page uses the industry-standard pitch multiplier formula (√(1 + (rise÷12)²)) to convert your flat footprint into actual sloped roof area. Material quantities include a customizable waste factor to account for cuts at ridges, hips, and eaves. Results are estimates — always verify with your supplier before ordering materials.
How to use a roofing calculator accurately
Start with the building footprint, then choose the roof style that matches your project. Use measured pitch when possible and keep waste at 10-15% for straightforward rooflines. Increase waste for hips, valleys, and dormers.
Common roofing estimate questions
Most homeowners and contractors want to know three things first: total roof squares, number of shingle bundles, and underlayment rolls. Each SpecCalc roofing tool returns all three outputs so you can build a material list quickly before requesting supplier quotes.