Roofing Calculator
A full takeoff for a gable roof — squares, bundles, underlayment and cap.
Roof
= 480" (40')
= 336" (28')
= 18" (1' 6")
Results update as you typeLive
Roofing · Result
CalculatedBUNDLES (INCL. 10% WASTE)
47 bundles of shingles
- Squares
- 15.25
- Product
- TruDefinition Duration
- Bundles / square
- 3
- Waste
- 10%
Waste allowance 10%
SUGGESTED DEFAULTChangeCoverage 98.4 ft2 per square and 3 bundles per square are the manufacturer's published figures, not the definition of a square
MFR SPECCode references & assumptions · 2
How this result is supported
- ASSUMPTIONWaste applies to shingles only; starter, cap and drip edge come from edge lengths. Underlayment uses the manufacturer's printed roll coverage — felt sheets print it with the lap already netted, synthetic sheets print the gross roll area — so lap the sheets per their instructions and allow for it where the printed figure is gross
- UNVERIFIED
- MFR SPECCoverage 98.4 ft2 per square and 3 bundles per square are the manufacturer's published figures, not the definition of a square
- PRIMARY-VERIFIED
What do these evidence labels mean?
- PRIMARY-VERIFIED
- directly supported by one authoritative primary source, quoted with section/page/figure
- CROSS-VERIFIED
- independently supported by two or more appropriate authoritative sources
- DERIVED
- mathematically derived from PRIMARY-VERIFIED values; the derivation is preserved in data and in code
- INTERPRETED
- a source exists but translating it into calculator behaviour required interpretation
- CONVENTION
- recognised trade practice, not a mandatory provision
- ASSUMPTION
- product/design assumption or useful default with no authoritative basis
- UNVERIFIED
- insufficient authoritative evidence
Code references and product data are quoted in the units their source uses.
Reference checks are informational, not compliance determinations.
How roofing is calculated
Give the building footprint and the pitch and the calculator does the whole takeoff: it works the sloped area from the plan area, adds the overhangs, converts to squares, and then reads the bundle count off the product you selected rather than off an average.
A gable and a hip over the same footprint have the same sloped area — the hip's four triangles reassemble into exactly the gable's two rectangles. What differs is the cap: the gable wants ridge only, the hip wants ridge and hips, and that is why the preset changes the accessory quantities without changing the area.
Every accessory is counted against its own product's printed coverage. Underlayment layers follow the pitch, because manufacturers double the layer on low slopes, and the calculator says which band it applied rather than leaving it to be discovered on site.
sloped area = plan area × slope factor
squares = sloped area ÷ 100
A roofing square is 100 ft².
bundles = ceil(squares × (1 + waste) × bundles per square)