Roofing Squares & Materials Calculator
One roofing square is 100 square feet of roof surface, and standard architectural shingles come three bundles to a square. A 2,000 square foot footprint under a 6:12 roof works out to about 22.4 squares before waste, or roughly 25 squares and 74 bundles once a 10 percent waste allowance is added.
The calculator below does that from either your building dimensions or a known area, then estimates underlayment, starter, ridge cap, drip edge and fasteners alongside it.
Use it to sanity-check a quote. Do not order materials from it. A real order comes off a measured roof plan with the actual coverage figures for the products being installed.
Turn a roof area (or just the building's dimensions) into roofing squares, then into the quantities a crew would actually order: bundles, underlayment, starter, ridge cap and fasteners. Useful for sanity-checking a quote. Not a material order.
Your Roof in Squares and Materials
Planning quantities for checking a quote against. A real material order comes off a measured roof plan.
What this means
Estimated quantities
What we assumed
What this does not include
Get a measured roof plan
We measure every plane, hip, valley and penetration and give you the real numbers: the ones a material order and a price are actually built from. It costs you nothing and it settles the size question for good.
Get Your Roof Measured Related: roof pitch calculator · roof cost calculatorHow this calculator works (formulas and sources)
- One roofing square = 100 square feet of roof surface. That is the unit roofers, suppliers and quotes are all built around.
- Footprint to roof area: footprint × pitch multiplier, where the multiplier is √(rise² + 144) ÷ 12. A 6:12 roof has a multiplier of about 1.118, so it has roughly 12% more surface than the ground it covers.
- Waste: 10% is the industry default cited in roofing guidance, with more for cut-up roofs and less for simple ones. Waste covers cuts, overlaps at hips and valleys, and starter runs. It is not a contingency for mistakes.
- Bundles: three bundles per square, which is standard for architectural laminated shingles: GAF Timberline HDZ covers 33.3 sq ft per bundle. Heavier premium products can run four or five bundles per square, so check the wrapper.
- Underlayment: synthetic rolls typically cover 10 squares, #15 felt about 4 squares and #30 felt about 2 squares per roll.
- Fasteners: roughly 64 shingles per square for a laminated product, at 4 nails each as standard or 6 in high-wind applications. Coil nails run about 120 per pound at typical roofing sizes, so we convert on that basis.
- Starter and ridge cap are reported in linear feet rather than bundles, because coverage per bundle differs so much between products that converting would be a guess. Take the linear footage to your supplier.
- Not modelled: multiple roof planes at different pitches, dormers, porch roofs, penetration cut-outs, ice-and-water shield, valley metal, and anything about the existing roof that has to come off first.
What a roofing square is, and why quotes use it
A roofing square equals 100 square feet of roof area. Roofers, suppliers and quotes are all organised around it, because it gives everyone a shared unit for discussing materials and labour. A roof measured at 2,800 square feet is 28 squares before any allowance for cuts and overlaps.
It is not the same as your home’s square footage. The roof covers a three-dimensional surface above the footprint, and the footprint itself often includes garages, porches and overhangs that the interior measurement leaves out. Two homes with similar living space can need very different amounts of roofing.
Waste is not padding
The waste allowance covers material that genuinely goes onto the roof but does not count as coverage: angled cuts at hips and valleys, overlaps at ridges, and the starter course along the eaves. Ten percent is the industry default starting point.
Simple roofs with long uninterrupted runs can come in under it. Cut-up roofs with multiple planes, dormers and several valleys routinely need more: 15 percent or higher. The shape of the roof influences this far more than a small difference in the area estimate does.
What these quantities do not include
- Ice-and-water shield at eaves, valleys and penetrations.
- Valley metal, step flashing, counter-flashing and pipe boots.
- Ventilation products: ridge vent, box vents and soffit intake are sized separately.
- Decking replacement. Rotten or delaminated sheathing is only found once the old roof is off.
- Tear-off, disposal and dumpster costs.
- Multiple roof planes at different pitches, dormers and porch roofs, which this model treats as a single shape.
- Product-specific coverage. Premium and designer shingles can run four or five bundles per square rather than three.
Why a satellite measurement is not the same as a plan
Satellite and aerial measurement reports are genuinely useful and generally accurate on simple roofs. They struggle with the things that drive waste: shallow dormers, roofs partly hidden by tree canopy, transitions between sections at different pitches, and additions that do not read clearly from above.
They also measure the roof as it appears, not as it will be built, which matters when decking has to be replaced, ventilation is being added, or a section is changing pitch. For a quote, a measured plan of every plane remains the standard.
Frequently asked questions
How many squares is my roof?
Take the footprint your roof covers, including overhangs, and multiply it by the pitch multiplier for your roof slope, then divide by 100. A 2,000 square foot footprint under a 6:12 roof is about 2,236 square feet of roof, or 22.4 squares before waste. The calculator above does this from either dimensions or a known area.
How many bundles of shingles are in a square?
Three, for standard architectural laminated shingles: GAF Timberline HDZ, for example, covers 33.3 square feet per bundle. Heavier premium and designer products can run four or five bundles per square, so check the wrapper before ordering rather than assuming three.
What waste percentage should I use for a roof?
Ten percent is the industry default starting point. A simple roof with long uninterrupted runs and no valleys can come in below it; a cut-up roof with multiple planes, dormers and several valleys often needs 15 percent or more. Waste covers cuts, overlaps and the starter course, not mistakes.
How much underlayment do I need?
It depends on the product. Synthetic underlayment rolls typically cover about 10 squares, #15 felt about 4 squares and #30 felt about 2 squares per roll. Note that on roofs between 2:12 and 4:12, manufacturers require a doubled underlayment layer, which halves the effective coverage per roll.
Can I use this to order materials?
No. These are planning quantities from a simplified model of the roof, useful for understanding a quote. A real order is built from a measured plan of every plane, with the manufacturer's actual coverage figures for the exact products being installed and allowances set by the person cutting them.