Roofing Calculator
Adjust the inputs below. Results update as you type.
How it works
Roof area = footprint area × pitch multiplier. Pitch multiplier for 6:12 pitch = √(6²+12²)/12 ≈ 1.118. One roofing square = 100 sq ft. Add 10–15% waste for gable roofs, 15–20% for hip roofs. Asphalt shingles: 3 bundles/square. Include underlayment, ridge cap, and drip edge in material orders. Labor averages $3–6/sq ft; total installed cost $5–12/sq ft depending on materials.
Input guidance
- Confirm date/time/unit settings before comparing outputs.
- If a task has optional fields, run both with and without them to understand impact.
- Save scenario variants when making practical decisions.
The formula
Roof area = footprint area × pitch multiplier (which accounts for slope). Materials are sold in squares (100 sq ft); add waste for cuts and ridges.
Worked example
A 1,500 sq ft footprint with a moderate pitch (multiplier ~1.12) is about 1,680 sq ft of roof, or roughly 17 squares plus waste.
More examples to test
- Quick-pass example: run default assumptions for a first estimate.
- Refined example: update one assumption at a time to isolate impact.
How to interpret results
Use outputs as operational estimates and pair them with local constraints, business rules, or provider requirements.
When this can be inaccurate
Utilities can miss local policy details, special-case rules, and environment-specific constraints.
Change history
- July 2026: Quality-reviewed for publication with formula checks and explanatory copy updates.
Site-wide corrections also appear on the corrections log.
Find productivity tools for everyday workflows
General recommendation, not professional advice.
Frequently asked questions
How do I measure roof area?+
Find the building footprint, then multiply by a pitch factor for the slope. Steeper roofs have more surface than the footprint suggests.
What is a roofing square?+
A unit equal to 100 square feet of roof area. Shingles and other materials are sold and estimated by the square.
How much extra should I order?+
Add about 10–15% for waste, cuts, hips, valleys, and starter courses so you do not run short mid-job.
Why are outputs slightly different from another tool?+
Different tools can use different rounding rules, default assumptions, and treatment of edge cases.
How can I improve estimate reliability?+
Use verified inputs from real records and re-run calculations after major assumption changes.
Guided next steps
Want the full workflow? Use this calculator inside a step-by-step guide.