Estimate roof surface area from plan dimensions and pitch, then calculate editable waste, roofing squares, shingles or panels, underlayment, and material cost.
Plan area is horizontal length times width. For pitched sections or known plan area, a rise-and-run slope factor converts plan area to roof surface area.
A directly measured roof surface area is not pitch-adjusted again. Waste is applied once before roofing squares and purchase units are calculated.
length × width × quantity√(1 + (rise ÷ run)²)atan(rise ÷ run), converted to degreesplan area × slope factorroof surface area × (1 + waste % ÷ 100)recommended ft² ÷ 100ceiling(roofing squares × bundles per square), or coverage-based purchase unitsA 40 × 30 ft plan at 6:12 has a 1.118034 slope factor and about 1,341.64 ft² of roof surface. With 10% waste it needs about 1,475.80 ft², 14.758 roofing squares, and 45 bundles at 3 bundles per square.
A flat 20 × 30 ft roof has 600 ft² surface area. With 10% waste it needs 660 ft², or 6.6 roofing squares and 20 bundles at 3 per square.
A known 200 m² roof surface becomes 220 m² with 10% waste. At 2.5 m² per panel, buy 88 panels.
Enter rise and run explicitly. A 6:12 pitch rises 6 units for every 12 horizontal units.
The editable 10% default is not universal; roof complexity, cuts, and product instructions affect extra material.
Bundle and panel coverage varies. Use the selected product's documented coverage when available.
One US roofing square equals exactly 100 ft² of roof surface. Roofing squares remain fractional; bundles are rounded upward independently. Three bundles per square is only an editable common example.
Underlayment uses roof surface area with its own editable extra percentage and manufacturer coverage per roll.
A centered two-sided gable using the full building footprint must not be doubled again before slope adjustment. This v1 calculator omits overhang presets and does not model hips, valleys, ridge caps, flashing, drip edge, or complex architecture.
Optional costs cover configured bundles, panels, roofing squares, and underlayment rolls only. Labor, tear-off, disposal, nails, flashing, ventilation, permits, taxes, and delivery are excluded.
Multiply horizontal plan dimensions and apply the rise/run slope factor.
Greater rise relative to run increases slope factor and roof surface area.
The roof rises 6 units for each 12 horizontal units.
The angle is arctangent of rise divided by run.
A US roofing square is 100 ft² of roof surface.
It varies by product; enter the manufacturer value. Three is only a common example.
Waste depends on geometry, cuts, and product guidance; the default 10% is editable.
Using the full building footprint, multiply it by slope factor without doubling the footprint again.
If dimensions exclude overhang, account for it in measured plan dimensions. This v1 has no automatic overhang model.
Yes, with editable roll coverage and a separate extra percentage.
No; those require linear measurements and installation details.
Yes, using user-entered coverage area per panel without layout optimization.
No. Cost is material-only.