Shingle Calculator
Bundles, squares and accessories against the product's own printed coverage.
Roof
Results update as you typeLive
Shingle · Result
CalculatedBUNDLES (INCL. 10% WASTE)
81 bundles
- Squares
- 26.40
- Underlayment
- 3 rolls · 1 layer
- Cap
- —
- Starter
- —
- Drip edge
- —
- 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
Product data, as published
Shingle: Owens Corning TruDefinition Duration — Owens Corning Section 073113, Fiberglass-Based Asphalt Shingles & Accessories (revision not recorded; retrieved 2026-09-04)
Underlayment: Owens Corning DeckDefense (10 sq) — Owens Corning Section 073113, Fiberglass-Based Asphalt Shingles & Accessories (revision not recorded; retrieved 2026-09-04)
- 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 shingle is calculated
Bundle counts come from the coverage printed on the product's own data sheet. Three bundles to the square is the common case and the calculator will tell you when that is what it used, but it is a property of the product rather than a rule, and the generic row is a unit definition rather than a real shingle.
Underlayment layer count follows the pitch. Manufacturers specify a doubled layer across their low-slope band, so the calculator applies it and names the band rather than leaving the difference to be found on the roof.
Starter, ridge cap and drip edge are counted against edge lengths, not against area, which is why a hip roof of the same size needs materially more cap. Enter the ridge and hip run and the cap follows from it.
squares = sloped area ÷ 100
bundles = ceil(squares × (1 + waste) × bundles per square)
courses = exposed length ÷ exposure
Exposure is the part of each shingle left showing.