/// Short answer
roof pitch ratio — the planning answer
Roof pitch describes vertical rise relative to horizontal run, commonly written as inches of rise per 12 inches of run. From measured rise, run, and horizontal span, a calculator can derive pitch ratio, angle, slope percentage, rafter length, and a surface multiplier. Verify the measurement reference and do not use geometry alone for structural, roofing, or access decisions.
How do you estimate roof pitch ratio?
Roof pitch describes vertical rise relative to horizontal run, commonly written as inches of rise per 12 inches of run. From measured rise, run, and horizontal span, a calculator can derive pitch ratio, angle, slope percentage, rafter length, and a surface multiplier. Verify the measurement reference and do not use geometry alone for structural, roofing, or access decisions.
Pitch = rise ÷ run. Rafter length follows the right triangle; surface area uses the sloped length multiplied by the measured run or eave length.
/// Continue with the numbers
Run the roof pitch calculator
Use the roof pitch calculator to convert rise and run into pitch per twelve, slope percent, angle, rafter multiplier, and a simple rafter length. These outputs describe entered geometry only; they do not select structural members. Confirm the actual run convention, overhangs, ridge details, loads, and approved roof design separately.
/// Keep the topic connected
Related calculators
Use the neighboring tools to keep each material, layer, and order assumption visible instead of hiding it inside one estimate.
What should you measure first?
Measure rise and run from a consistent reference, or use a verified roof plan. Record whether the span is one-side horizontal run or a full building width.
- Record rise and horizontal run in the same unit basis.
- Clarify one-side span versus full building width.
- Note overhangs, hips, valleys, dormers, and measurement access.
What should you verify before ordering?
Roof structure, decking, slope limits, flashing, ventilation, wind, snow, fire, and safe access require professional review.
- Cross-check pitch from a second measurement.
- Use the result as geometry for material estimating only.
- Keep roof material coverage and waste as separate inputs.
/// Continue the workflow
Related ProjectQty pages
/// Field-ready worksheet
Download the measurement checklist
Use the worksheet to record dimensions, product-label values, and verification notes locally. ProjectQty does not receive or store your project inputs.
/// Evidence trail
Sources and assumptions
This article inherits the calculator's declared source scope. Product yields, coverage, density, and label rates should be replaced with the exact product selected for the job.
Exact international-foot to meter conversion; U.S. survey-foot conversion is explicitly outside this claim.
NOAA National Geodetic Survey · Prequalified fallbackThe DSDATA Format, Appendix D: U.S. Survey Foot vs International FootIndependent confirmation that one international foot equals exactly 0.3048 meters; U.S. survey-foot conversion remains distinct.
/// Common questions
Roof Pitch Ratio: Rise, Run, Angle, and Rafter Length FAQ
What does a 6-in-12 roof pitch mean?
It means the roof rises 6 units vertically for every 12 units of horizontal run, using the same unit basis.
Does pitch equal roof angle?
No. Pitch is a rise-to-run ratio; angle is the arctangent of that ratio. They describe related but different values.
Does this calculate a safe roof?
No. It calculates geometric values from entered measurements and does not assess structure, code, or safe access.