About & methodology

Roofing Calculator is a free tool that estimates how much roofing material a roof needs — in squares and bundles — and what it costs, from the building footprint and roof pitch. No sign-up; the math runs in your browser.

How it works

• Roof area = footprint × pitch multiplier, where the multiplier = √(rise² + 12²) ÷ 12 (a 6/12 pitch is ~1.12).
• Roofing squares = roof area ÷ 100, plus a 10% waste allowance.
• Bundles = squares × bundles-per-square (3 for most asphalt shingles).
• Cost = roof area (in squares) × a per-square installed range for the material.

Important

These are planning estimates for a simple roof. Hips, valleys, dormers, steep pitch, tear-off of the old roof, and local labor rates all move the real numbers. Confirm with a licensed roofer before ordering.