Work out roofing material and cost with our free calculator. Get bundle count, underlayment rolls, drip edge, ridge cap, and total installed price fast.
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Roofing bids live and die on the materials takeoff. Miss the pitch multiplier and your shingle count is short by 20%. Forget the waste factor and you’re making a mid-job run to the supply house. This roofing calculator handles the geometry and the materials in one pass. Pick your roof type (gable, hip, shed, gambrel, mansard, or direct area). Enter building length, width, and pitch. The tool returns roof surface area, squares, and every downstream quantity: bundles of shingles, rolls of underlayment, drip edge, ridge cap, valley flashing, starter strip, and fasteners. Twelve roofing presets load the right coverage-per-bundle for each material. Add unit costs and you get a total installed estimate plus cost per square, which is how suppliers quote. Contractors use it for bids. Homeowners use it to check a quote before signing.
Choose your currency. Sixteen options, including USD, EUR, GBP, and INR.
Pick imperial or metric. Every input and output follows that choice.
Select a roof type. Gable, hip, shed, gambrel, mansard, or direct area entry.
Enter building length and width. Skip this if you’re using direct area mode.
Set the roof pitch. Rise:12, degrees, or percent all work.
Add the overhang. Twelve inches is typical.
Choose a roofing preset. Asphalt, metal, tile, slate, shake, or membrane.
Set waste factor and coverage per bundle. Presets fill these automatically.
Toggle drip edge, ridge cap, valley flashing, and starter strip. Set underlayment type.
Enter unit costs and read the summary. The result panel shows bundles, squares, and total cost.
Roof area drives everything. The tool converts your building footprint to plan area, adds overhangs, then multiplies by the pitch factor.
Formula: Roof Surface Area = Plan Length × Plan Width × √(1 + Pitch²)
Formula: Squares = Roof Surface Area ÷ 100 ft² (or 9.29 m²)
Formula: Area with Waste = Roof Area × (1 + Waste % ÷ 100)
Formula: Bundles Required = Ceiling(Area with Waste ÷ Coverage per Bundle)
Formula: Total Fasteners = Squares Required × Fasteners per Square
Plan length is building length plus two overhangs. Plan width is building width plus two overhangs. Pitch is the rise over 12 expressed as a decimal. The pitch multiplier is the hypotenuse formula applied to the pitch ratio.
For a gable roof, ridge length equals plan length and eave length is twice plan length. Hip roofs shorten the ridge by the building width and have no rake. Shed roofs have one eave and no ridge. Gambrel and mansard use multipliers that reflect their two-slope geometry.
Bundle count comes from area with waste divided by the coverage per bundle. Asphalt shingles cover about 33.3 ft² per bundle. Clay tile covers about 10 ft². Standing seam covers a full square per roll. The preset dropdown handles these differences.
Underlayment rolls divide roof area by coverage per roll. Fasteners multiply squares by a per-square rate. Trim lengths come from the ridge, eave, and valley geometry.
A 38-foot by 26-foot gable roof at 8:12 pitch with 18-inch overhangs. Architectural shingles (33.3 ft² per bundle). 10% waste. Synthetic underlayment, 1,000 ft² per roll. 3 tabs per square for fasteners.
Step 1 — Plan dimensions. Length = 38 + 3 = 41 ft. Width = 26 + 3 = 29 ft.
Step 2 — Pitch ratio. 8/12 = 0.6667. Multiplier = √(1 + 0.4444) = √1.4444 = 1.2019.
Step 3 — Roof area. 41 × 29 × 1.2019 = 1,428.9 ft².
Step 4 — Squares. 1,428.9 ÷ 100 = 14.29 squares.
Step 5 — Area with waste. 1,428.9 × 1.10 = 1,571.8 ft².
Step 6 — Bundles. 1,571.8 ÷ 33.3 = 47.2, rounded up to 48 bundles.
Step 7 — Ridge length. 41 ft. Eave length = 2 × 41 = 82 ft. Rake length = 4 × slope of half-width. Half-width = 14.5 ft. Slope = √(14.5² + 9.67²) = √(210.25 + 93.5) = √303.75 = 17.43 ft. Rake = 4 × 17.43 = 69.7 ft.
Step 8 — Underlayment. 1,428.9 ÷ 1,000 = 1.43, rounded to 2 rolls.
Step 9 — Fasteners. 14.29 squares × 320 per square = 4,573 fasteners. Boxes = ceil(4,573 ÷ 5,000) = 1 box.
Step 10 — Cost at $34 per bundle, $120 per underlayment roll, $2.50/ft drip edge, $6/ft ridge, $4/ft starter, $45 per box of fasteners, $9 per sealant tube (4 tubes).** Shingles = 48 × 34 = $1,632. Underlayment = 2 × 120 = $240. Drip edge = 82 × 2.50 = $205. Ridge = 41 × 6 = $246. Starter = 82 × 4 = $328. Fasteners = 1 × 45 = $45. Sealant = $36. Material subtotal = $2,732. Labor at $1.75/ft² = 1,428.9 × 1.75 = $2,500.58. Total = $5,232.58.
Interpretation: Order 48 bundles of architectural shingles, 2 rolls of synthetic underlayment, and 1 box of fasteners. Material runs about $2,700 before labor. At $5,232 total, cost per square is $366, which sits in the typical range for architectural asphalt installed.
Divide area with waste by 33.3 ft² per bundle and round up. A 15-square roof with 10% waste needs about 50 bundles. Three bundles cover one square for asphalt shingles.
Multiply plan length by plan width, then multiply by the pitch multiplier. Add overhangs to length and width first. A 30×40 building with 12-inch overhangs and a 6:12 pitch has a roof area of about 1,502 ft².
100 square feet of roof surface. Shingles are sold in bundles of three per square. A 20-square roof needs 60 bundles before waste.
Asphalt shingles installed: $350 to $550 per square. Architectural: $450 to $700. Standing seam metal: $900 to $1,800. Clay tile and slate run higher. A 15-square roof with architectural shingles typically lands between $7,000 and $10,000.
10% for a simple gable roof. 15% for a hip roof or one with valleys. 20% for complex roofs with dormers and multiple pitch changes.
Yes. Underlayment is required by code in most jurisdictions and provides a secondary water barrier. Synthetic underlayment is standard. Peel-and-stick is used at eaves and valleys in cold climates.
An L-shaped metal strip along eaves and rakes. It keeps water from wicking back under shingles and protects the fascia. Most codes require it. The calculator includes eave-only drip edge length by default.
320 nails per square for hand-nailing. High-wind areas require six nails per shingle instead of four, which pushes the count to about 480 per square.
A ridge cap with a vent channel that lets hot air escape from the attic. Vented ridge is code-required in many jurisdictions. It installs the same way as a standard ridge cap.
Measure 12 inches horizontally along the roof, then measure the vertical rise. The ratio of rise to 12 is your pitch. Six inches of rise over 12 inches of run is 6:12.
Sometimes. Building codes usually allow a second layer if the existing roof is in good shape and the structure can handle the weight. Strip the old roof if it has two or more layers already, or if it’s curling or damaged.
Asphalt: 15 to 30 years. Architectural asphalt: 25 to 40. Standing seam metal: 40 to 70. Clay tile: 50 to 100. Slate: 75 to 150. Climate, ventilation, and installation quality all affect lifespan.
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