How to use
- Enter one repeated roof section size and the number of similar sections.
- Enter pitch as rise per 12 inches of run.
- Review squares, bundles, and underlayment roll count as planning estimates.
Input guide
- Pitch rise is the first number in a pitch such as 6/12.
- A roofing square is 100 sq ft.
- Bundles per square is commonly 3 for many shingles, but product labels vary.
Common mistakes
- Using flat footprint area without pitch factor.
- Ignoring valleys, hips, dormers, waste, starter, and ridge cap.
- Treating a roof estimate as safety or code advice.
Assumptions and limitations
- No safety, structural, flashing, permit, ventilation, or code guidance is included.
- Complex roofs need professional takeoff and verification.
- Starter shingles, ridge caps, flashing, nails, and disposal are not quantified.
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Formula
- Footprint area = roof section length x width x number of sections.
- Pitch factor = square root of 12 squared plus pitch rise squared, divided by 12.
- Roof area = footprint area x pitch factor.
- Bundles = roofing squares x bundles per square.
Example
A 30 ft x 20 ft roof section at 6/12 pitch has about 671 sq ft of roof area. With 10% waste, estimate 8 squares and 24 bundles at 3 bundles per square.
FAQ
Can I use this for a complex roof?
Use it only as a rough planning aid. Complex roofs with valleys, dormers, hips, and multiple slopes need detailed takeoff.
What is a roofing square?
One roofing square is 100 square feet of roof surface area.