Verified engineering tool for reliable rafter design estimates using standardized formulas
Mathematically checked calculations based on industry-standard engineering principles
Enter your roof parameters on the left and click "Calculate" to generate engineering estimates.
Results will include:
This tool uses standard simply-supported beam formulas for uniform loads. Complex geometries, concentrated loads, or non-standard conditions require professional engineering review.
Material properties are based on industry averages. Actual lumber strength can vary by grade, moisture content, and manufacturer. Always verify with material specifications.
This calculator provides rafter sizing only. Proper connection design (fasteners, hardware, bearing surfaces) must be designed separately by qualified professionals.
Local building codes may impose additional requirements beyond these calculations. Always verify with local jurisdiction requirements and obtain necessary permits.
For spans over 20ft, commercial structures, occupied spaces, or critical applications, professional engineering verification is essential before construction.
Actual construction must account for site-specific factors including wind exposure, seismic considerations, soil conditions, and construction tolerances.
Provide precise measurements for span, run, and rise based on actual site conditions. Double-check measurements before calculation.
Select materials and loads conservatively. When in doubt, choose stronger materials or higher load categories for safety margins.
Examine strength achievement percentages and deflection results. Values below 100% require redesign or professional consultation.
Use results as guidance, not final design. Implement with proper connections, verify local codes, and maintain construction quality control.