Roofing Calculators

How Rafter Length Is Calculated (Pythagorean Theorem Plus Overhang)

Rafter length is the Pythagorean hypotenuse of a roof's run and rise, with the eave overhang simply added on afterward — the roof slope itself is a right triangle, so the same theorem taught in basic geometry gives the exact length of lumber needed, before accounting for the extra length that hangs past the wall line.

How Roofing Material Quantity Is Calculated (Why Sloped Area Beats Footprint)

A sloped roof's actual surface area is always larger than its flat footprint (length × width) — dividing the footprint by the cosine of the roof's slope angle gives the true surface area that needs covering, and skipping this step is one of the most common ways people underestimate roofing material.

Understanding Roof Pitch: X-in-12, Degrees, and Slope Percent Explained

Roof pitch is the same rise-over-run ratio expressed three different ways — the traditional "X-in-12" construction notation, an angle in degrees, and a slope percentage — and converting between them is just a matter of which form a given trade or document happens to use, not three different measurements of the roof.