The roofing guides

• How to Measure Roof Pitch: Every Method, and How Each One Goes Wrong - Measure roof pitch five ways: a 12 in level and tape in the attic, on the shingles, off a rake board, sighted from the ground, or with a phone.
• Roof Pitch to Degrees: Converting Both Ways, With the Full Chart - 6/12 pitch is 26.57 degrees and a 50 percent grade. Convert pitch to degrees with arctan and back again, with a full chart from 1/12 to 24/12.
• Roof Slope Factor: What It Is, the Full Table, and How Estimators Use It - The roof slope factor is 1 / cos(angle): multiply a flat footprint by it for real roof area. Table for every pitch, plus a 2,400 sq ft example.
• Roof Pitch Chart: Degrees, Percent Grade, Slope Factor and Hip/Valley Factor - Roof pitch chart from 1/12 to 24/12 with degrees, percent grade, slope factor and hip/valley factor, plus degrees back to x/12 and area tables.
• How to Calculate Roof Area: From Footprint to Roofing Squares - Multiply each roof plane's flat footprint by its own slope factor, total it, then divide by 100 for squares. Worked examples, a squares table and waste.
• Minimum Roof Pitch by Material: IRC Minimums, Low Slope and What You Can Actually Put On a Given Slope - Minimum roof pitch by material: shingles 2/12, tile 2.5/12, slate 4/12, membrane 0.25/12. IRC minimums, the low slope line, and what governs.
• Rafter Length Calculator: Common, Hip and Valley Rafters, With Worked Examples - Rafter length is run times the slope factor, and run is half the span. Worked 6/12 gable and hip examples, plus per-foot-of-run tables.
• Walkable Roof Pitch: How Steep Is Too Steep to Walk? - No pitch is safe by itself. Up to about 6/12 most people walk a dry roof, 7/12 to 9/12 wants roof jacks, 10/12 and up is staged work.