Understanding the calculator’s limits
This calculator describes geometry; it does not assess the safety or suitability of a roof.
Measurements and assumptions
Use measurements from the same straight slope. Run is a horizontal projection. The geometric rafter excludes overhang, joints, cuts and construction allowances. An inclination without a known length cannot determine physical dimensions.
Precision and interpretation
Display precision rounds the answer without changing the stored measurements. Check units and source dimensions. A diagram is a visual aid; use the numerical results for dimensions, especially for very small or steep angles.
Construction decisions
Loads, materials, connections, local requirements and roof-covering suitability require project-specific information and qualified judgement. The calculator provides no structural sizing, certification or compliance approval.