What type of roof do you have?
Identifying your roof shape is the first step to an accurate material estimate — each type breaks into planes differently and carries a different waste factor. Match your roof to one of the diagrams below, then follow the estimating note straight into the calculator.
Gable roof
The most common roof shape: two sloping planes that meet at a central ridge, forming a triangle at each end. If your roof looks like an upside-down V from the front, it is a gable.
How to estimate it: A gable is just two rectangles of equal size. Measure one plane's length and width, enter it as a section, set the pitch, then add a second identical section — or double the area. This is the easiest roof to estimate accurately.
Estimate a gable roof →Hip roof
All sides slope downward toward the walls, with no vertical gable ends. A square hip roof meets at a point; a rectangular one has a short ridge at the top with sloped triangular ends.
How to estimate it: A hip roof is two trapezoids plus two triangles (or four triangles if it peaks at a point). Measure each face separately as its own section. Hip roofs waste more material at the hips, so lean toward a 15–20% waste factor.
Estimate a hip roof →Gambrel (barn) roof
The classic barn shape: each side has two slopes — a shallow upper slope and a steep lower one — to maximize headroom in the space below. Common on barns, Dutch Colonial homes, and sheds.
How to estimate it: Each side is two planes with different pitches, so measure four sections total (upper and lower on each side). Enter each with its own pitch — the steep lower slopes have a very different multiplier from the shallow top.
Estimate a gambrel →Mansard roof
A French-style roof with four steep, almost-vertical lower sides and a low-slope or flat top, often with dormer windows. It maximizes top-floor living space.
How to estimate it: Treat the steep sides and the flat top separately. The near-vertical sides have a high pitch multiplier and the top is nearly flat — entering them as one pitch will throw the estimate off badly. Measure each face as its own section.
Estimate a mansard roof →Shed (skillion) roof
A single flat plane that slopes in one direction, with no ridge. Common on modern homes, additions, porches, and sheds.
How to estimate it: A shed roof is the simplest case: one rectangle, one pitch. Measure length and width, enter a single section, and set the pitch. No ridge or hip waste to worry about, so 10–12% waste is usually plenty.
Estimate a shed →Flat / low-slope roof
Appears level but actually has a slight slope (often 1:12 to 2:12) for drainage. Common on modern, commercial, and some ranch-style buildings.
How to estimate it: Measure the footprint as a single rectangle; at very low slopes the pitch multiplier is close to 1, so true area ≈ footprint. Note that asphalt shingles need at least a 2:12 pitch — below that, a membrane roof is required, not shingles.
Estimate a flat / low-slope roof →Still not sure?
Most homes are a gable, a hip, or a combination of both with dormers. When in doubt, use the full calculator's multi-section builder: add one section per visible roof plane, give each its own pitch, and the take-off adds them up. If you are unsure of a plane's pitch, the pitch calculator has a visual slider and a measure-it-yourself diagram.