Roofing calculator
Enter your roof footprint and pitch. You'll get the actual sloped roof area, the number of roofing squares, and how many bundles of shingles to order — instantly.
Measure the area the roof covers on the ground, including the overhangs — not the walls.
Order about 132.8 m² (14.30 squares, 43 bundles) to allow ~10% for waste, ridge and hip caps, and offcuts.
Roof area = footprint × slope factor for your pitch (here ×1.118). A square is 100 ft² of roof; bundle counts assume standard asphalt shingles at about 3 bundles per square. Tiles, metal and specialty shingles cover differently — confirm the coverage printed on the product before you order.
Common questions
- How do I calculate how much roofing I need?
- Measure the footprint the roof covers on the ground (length × width, including overhangs), then multiply by the slope factor for your pitch to get the actual sloped area. A 40 ft × 30 ft footprint at a 6:12 pitch is 1,200 ft² flat × 1.118 ≈ 1,342 ft² of roof — about 13.4 squares. Add roughly 10% for waste.
- What is a roofing square?
- A square is the roofing industry's unit for 100 square feet of roof surface, used across the US and Canada. Shingles, underlayment and labour are all quoted per square, so converting your area to squares is the first step in pricing a job: 1,342 ft² of roof is 13.42 squares.
- How many bundles of shingles are in a square?
- Most standard asphalt shingles — both 3-tab and architectural — cover one square in about 3 bundles, so a 13.4-square roof needs roughly 40 bundles. Heavier designer shingles can need 4 or 5 bundles per square, so always check the coverage printed on the wrapper before ordering.
- How much extra roofing should I order for waste?
- About 10% on a simple gable roof, rising toward 15% on a complex roof with lots of hips, valleys and cuts. The waste covers the starter course, ridge and hip caps, offcuts and the odd damaged shingle. The calculator shows the with-waste figure alongside the bare area.
- Does roof pitch change how much material I need?
- Yes — a steeper pitch means more surface over the same footprint. The footprint sets the plan area; the slope factor (√(rise² + 12²) ÷ 12) scales it up. A flat roof has a factor of 1.0, a 6:12 about 1.118, and a 12:12 about 1.414 — so a 45° roof needs roughly 40% more material than its footprint alone suggests.
- Is this a shingle calculator?
- Yes. After it works out the roof area and the number of roofing squares, it converts that into how many bundles of shingles to order (about three bundles per square for standard asphalt shingles), so it works as a shingle calculator — confirm the exact coverage printed on your shingle packaging.
Need the steeper-pitch numbers first? Use the roof pitch calculator → or read the roofing guide →
Reference & education only. Not professional, engineering, or code-compliance advice. Estimates are based on published model codes; local amendments and your Authority Having Jurisdiction (AHJ) govern. Always verify against the current adopted code and a licensed professional before doing work.
Last reviewed 2026-06.