Free · runs on this device · planning numbers
Roofing Calculator (Squares & Shingles)
Enter the building footprint and roof pitch to get the sloped roof area, the squares, and the shingle bundles to order, with waste. Also searched as the roofing squares calculator, shingle calculator, or roofing material calculator.
Formula
How the Math Works
Roof ft² = footprint ft² × √(1 + (rise ÷ 12)²) · Squares = roof ft² × (1 + waste %) ÷ 100 · Bundles = ⌈squares × 3⌉
Worked example: a 40 ft × 30 ft footprint (including overhangs) with a 6/12 pitch and 10% waste.
- 40 ft × 30 ft = 1,200 ft² footprint
- 6/12 multiplier = √(1 + 0.5²) = 1.118, so 1,200 × 1.118 = 1,342 ft² of roof
- Add 10% waste: 1,342 × 1.10 = 1,476 ft², which is 14.76 squares (order 15)
- 14.76 × 3 = 44.3, so 45 bundles
Units & assumptions
Measure the footprint in feet and include the eave and rake overhangs. Pitch is inches of rise per 12 in of run (enter 6 for a 6/12 roof). The multiplier assumes a single pitch over the whole roof. 1 square = 100 ft² of roof. Bundles assume 3 per square, which is typical for 3-tab and most architectural shingles. Some heavy shingles run 4–5 per square, so check the wrapper. Starter, ridge cap, underlayment, and flashing are not included.
Planning tool, not a PE stamp. Your spec, drawings, and supplier still win.
Field Questions
What is a roofing square?
One roofing square is 100 square feet of roof surface. A 1,476 ft² roof (with waste) is 14.76 squares, and you'd order 15.
How many bundles of shingles are in a square?
Usually 3 bundles per square for 3-tab and most architectural shingles. Some heavier designer shingles need 4 or 5 bundles, so check the coverage printed on the wrapper.
How do I use roof pitch to get roof area?
Multiply the footprint area by the pitch multiplier √(1 + (rise ÷ 12)²). The multiplier is 1.054 for 4/12, 1.118 for 6/12, 1.202 for 8/12, and 1.414 for 12/12.
How much waste should I add for shingles?
About 10% is a common allowance for a simple gable roof. Roofs with hips, valleys, and dormers often need about 15% or more because of cuts. Starter strip and ridge cap are figured separately.