How this instrument works
Roofers measure surface coverage in 'squares' rather than plain square footage — a square is simply 100 sq ft of coverage, a universal unit used industry-wide for estimating and ordering material regardless of the structure's actual shape. This instrument's first step just divides the entered surface area by 100 to get that square count.
Shingles themselves are packaged in bundles, and most popular asphalt shingle products — the majority of 3-tab and many architectural styles — are packaged so that 3 bundles cover exactly one square. That figure is disclosed as typical rather than universal: some heavier or specialty architectural shingle lines package 4 or even 5 bundles per square because the shingles themselves weigh more per bundle, so always check the specific product's own packaging before ordering, and adjust the Bundles per square field if it differs from 3.
The figure entered here should be the TRUE sloped surface area of the structure, not the flat footprint of the house beneath it — a pitched surface always covers more surface than the building's footprint suggests, since steeper pitches add real coverage. This site's own roofing area instrument (which factors in pitch) or a roof-pitch and rafter-length calculation can supply that true sloped figure if you're starting from a footprint rather than a known surface figure.
- Enter Roof area (sq ft) — the TRUE sloped roof surface area, not the flat building footprint.
- Adjust Bundles per square if your specific shingle product packages differently than the standard 3 — check the product's own label.
- Read Roofing squares (area ÷ 100) and Bundles needed beneath the inputs.
- Add your own waste allowance for cuts, hips, valleys and ridge caps separately — this figure covers flat coverage only.
Worked example — a 2,000 sq ft roof, standard 3-bundle shingles
Enter 2000 into Roof area (sq ft) and leave Bundles per square at its default of 3 — the standard packaging for most 3-tab and many architectural asphalt shingles. Roofing squares reads 20.00, simply 2,000 divided by 100.
Bundles needed reads 60 — 20 squares times 3 bundles per square. That's the flat-coverage bundle count for this structure's true sloped area; a real material order would typically add a waste allowance on top of this figure for cuts along hips, valleys, ridges and edges.
Questions
What is a roofing 'square'?
A square is simply 100 sq ft of coverage — a standardized unit the roofing industry uses for estimating and ordering material regardless of a structure's actual shape or size. It has nothing to do with the building's geometric shape; a 20-square roof just means 2,000 sq ft of surface, whatever shape that surface happens to be.
How many bundles of shingles come in a square?
Most popular 3-tab and architectural asphalt shingles are packaged so 3 bundles cover one square (100 sq ft), but this isn't universal — some heavier architectural or specialty shingle lines package 4 or 5 bundles per square because their individual shingles weigh more. Always check your specific product's packaging or the manufacturer's coverage rating rather than assuming 3 applies to every shingle line.
Does 'roof area' mean the house's footprint or the actual sloped surface?
The true sloped surface area, which is always larger than the building's flat footprint once any pitch is factored in — a steeper structure covers noticeably more surface than a flatter one over the same footprint. This site's roofing area instrument (which factors in pitch) can convert a known footprint into that true sloped figure if you're starting from the footprint instead.
How much extra should I order for waste?
This calculator returns flat coverage only, with no waste allowance built in — a real order typically adds extra on top to cover cuts at hips, valleys, ridges, and edges, along with starter strip and ridge cap shingles which are often sold separately from field shingles. A common practice is adding roughly 10 percent for a straightforward job, more for a complex one with many hips and valleys.
How many individual shingles are in a bundle?
It varies by product — a bundle commonly holds somewhere between about 15 and 29 individual shingles and weighs roughly 50 to 80 lb, depending on the shingle's size, style, and weight class. The bundle count itself isn't what matters for ordering purposes though; the bundles-per-square coverage figure is what determines how much material a given surface actually needs.