How to use this calculator
- Enter House length in ft.
- Enter House width in ft.
- Enter Roof pitch.
- Press Calculate. The highlighted row is your order quantity; the note beneath it translates the number into real-world terms.
Formula & constants
True roof area = footprint × pitch multiplier (4:12 → 1.054, 6:12 → 1.118, 8:12 → 1.202, 12:12 → 1.414). One roofing square = 100 sq ft. Add 10–15% waste for ridges, valleys and starters. Every default in the fields above is editable — when your supplier’s spec sheet lists a different density, coverage rate or price, enter that number instead. The waste and compaction allowances follow common trade practice; see our methodology page for the derivation of each formula and the standards it references.
Where this fits in the project
Roof takeoffs start from the footprint corrected by pitch: get true area from the roof square footage calculator, convert to squares, then to shingle bundles or metal panels. Size gutters from the same perimeter measurement.
How this connects to your project
No quantity stands alone — each material in the chain depends on the ones around it. These are the planning steps that pair with the roofing calculator:
- Roof Pitch Calculator — Roof pitch affects surface area calculation.
- Roof Square Footage Calculator — Roofing calculator estimates squares from footprint and pitch.
- Shingle Calculator — Shingles are the most common roofing material.
- Roof Truss Calculator — Trusses form the roof framework.
- Roofing Cost Calculator — Estimate total roofing cost from squares calculated.
- Metal Roofing Calculator — Metal roofing is an alternative to shingles.
- Gutter Calculator — Gutters are installed along the roof edge.
- Siding Calculator — Roofing covers the top; siding covers the walls.
Frequently asked questions
What is a roofing square?
100 sq ft of roof surface — the unit all roofing materials and labor are priced in.
Why multiply by a pitch factor?
The footprint measures the horizontal projection; the sloped surface is longer. Steeper pitch, bigger multiplier.
How much waste on a roof?
10% on simple gables, 15%+ on hips and cut-up roofs with valleys and dormers.
Last verified: — prices reflect current national averages. See our methodology.
Estimates are for planning. Material densities, coverage rates and prices vary by region and supplier — confirm final quantities before ordering, and check local code where structural or electrical work is involved.