Free Roofing Shingles calculator with clear step-by-step results.
Shingle orders have four separate components. The field is area over bundle coverage with waste, ridge and hip caps come out of dedicated bundles covering roughly eight metres each, starter strip runs along the eaves, and valleys need flashing with a length allowance for laps.
Field bundles
Bundles = ceil(sloped area x (1 + waste) / coverage per bundle)
Cap bundles
Bundles = ceil(ridge and hip length / 8 metres per bundle)
Hips, valleys, rake edges and cap cutting all generate offcuts. A simple gable roof can manage 8%; a cut-up roof with dormers can exceed 15%.
Three-tab shingles can be cut into caps, but architectural laminated shingles cannot - they are too thick to fold over the ridge and need purpose-made caps.