Roofing Material Calculator
Roof squares, shingle bundles, underlayment, and nails from footprint and pitch.
Written by Golam Rabbani, Founder & Lead Engineer
How to use this roofing material calculator
- Toggle imperial (ft) or metric (m) for the dimensions.
- Enter the house footprint length and width (the ground-level projection of the roof).
- Enter the roof pitch as the rise per 12 — e.g. 6 means 6/12.
- Pick the shingle type and a waste percentage (10% straight, 15% complex roofs).
- Press Calculate to see squares, bundles, underlayment rolls, and nails.
About this roofing material calculator
The roofing material calculator converts a house footprint and roof pitch into the true sloped roof area, then estimates shingle bundles, underlayment rolls, and roofing nails. The pitch multiplier — √(1 + (rise/run)²) — accounts for the fact that the actual roof surface is longer than the ground projection. A 6/12 pitch multiplier is 1.118; a 12/12 (45°) is 1.414. The area with waste is divided by 100 ft² to get 'squares', the standard roofing unit. Each shingle type lists its bundles-per-square: 3 for standard 3-tab or architectural, 4 for premium asphalt and wood shake.
Worked example: a 40 ft × 30 ft footprint with a 6/12 pitch and architectural shingles. Footprint area = 1200 ft². Pitch multiplier ×1.118 → true roof area = 1342 ft². Add 10% waste → 1476 ft². That is 14.76 squares. At 3 bundles per square (architectural), you need 45 bundles. Underlayment: 1476 ÷ 400 ft² per roll = 4 rolls. Roofing nails: 14.76 × 320 nails/square ≈ 4720 nails.
Order a full extra bundle for ridge caps if you are not buying pre-cut ridge shingles, and add starter-strip shingles (1 bundle per ~120 linear feet of eave). Steep-slope roofs (above 9/12) and complex roofs with many hips, valleys, and dormers can push waste to 15–20%. Re-roofs that strip down to deck plywood may also need extra felt paper, ice-and-water shield at eaves, and step flashing — none of which the calculator quantifies.
FAQ
- How many shingles in a bundle?
- A standard 3-tab or architectural bundle covers ~33.3 ft² (3 bundles to a 100 ft² square). Heavy/designer shingles run 4 bundles per square. Bundle weight is typically 60–80 lb.
- What is a "roofing square"?
- 100 square feet of roof area. Shingle and underlayment quantities are quoted in squares because the unit divides cleanly into typical packaging.
- How do I measure roof pitch?
- Hold a level horizontal against the roof, then measure straight down from the 12-inch mark to the roof surface. That measurement (in inches) is the rise. A 6-inch rise over 12 inches is a 6/12 pitch.
- How much waste should I plan for?
- 10% for a simple gable roof. 15% for hip roofs or complex shapes with valleys, dormers, and skylights. Cuts at hips and valleys are the biggest source of waste.
- Does this calculator include flashing and ridge caps?
- No — it covers field shingles, underlayment, and nails. Add step flashing (one piece per shingle course where the roof meets a wall), ridge cap shingles, and ice-and-water shield separately.
- Is this calculator free?
- Yes — completely free, no signup, runs locally in your browser.