Shed Roof Calculator

Lean-To, Carport, Patio Cover and Small Gable Roofs

A shed roof is one sloping plane, which makes it the simplest roof to build and the easiest to get wrong on paper. This calculator takes the width and depth of the structure plus your chosen pitch and returns the rafter length including the overhang tail, the total rise across the span, the rafter count at your spacing, the roof surface area in square feet and roofing squares, the number of four by eight sheathing sheets, and the covering quantity for asphalt shingles, metal panels or rolled roofing. Switch to the gable option and it splits the depth into two runs and doubles the sloped surface. Because the whole rise happens across the depth on a lean-to, the high wall grows quickly as the pitch increases, and the tool shows that rise in inches so you can frame the tall side correctly. It also flags when your chosen pitch falls below the practical range for shingles. Works equally for carports, patio covers, garage lean-tos and small workshop roofs.