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Free online Roof Framing Calculator to easily calculate rafter length, pitch, and spacing for sheds, homes, and lean-to roofs. Fast & accurate results.
Roof framing is one of the most important aspects of any building project. Whether you’re constructing a house, shed, or lean-to roof, getting accurate rafter and pitch calculations is crucial for safety, durability, and appearance. That’s why we developed the Roof Framing Calculator a 100% free, easy-to-use tool designed to help homeowners, DIYers, and contractors calculate everything needed for perfect roof framing.
Our tool simplifies complex roof geometry and gives instant results for rafter length, rise, run, slope, pitch, and spacing. Whether you need a lean to rafter calculator, shed roof calculator, or a full roof truss calculator, our tool does it all in one place.
Roof framing refers to the process of constructing the structural skeleton of a roof using rafters, trusses, and beams. It includes the layout, design, and measurement of various elements that support the roof covering. Proper framing ensures your roof can handle the load of roofing materials and environmental factors like snow, wind, or rain.
Using our calculator is straightforward. You just need to enter the following:
After submitting, the calculator instantly provides:
This makes it perfect for those asking, "How do I calculate how many roof rafters I need?" or "How far can a 2x6 roof rafter span?"
Here are the core formulas used in our calculator, simplified for easy understanding:
1. Rafter Length Formula (Pythagorean Theorem):
Rafter Length = √(Rise² + Run²)
2. Rise Calculation (based on pitch):
Rise = Run × Pitch Ratio
3. Run Calculation:
Run = (Total Span ÷ 2) - Overhang
4. Total Number of Rafters:
Number of Rafters = (Span ÷ Rafter Spacing) + 1
5. Roof Pitch Conversion Chart:
| Pitch Ratio | Degrees | Rise (per foot of run) |
|---|---|---|
| 2/12 | 9.46° | 2 inches |
| 4/12 | 18.43° | 4 inches |
| 6/12 | 26.57° | 6 inches |
| 8/12 | 33.69° | 8 inches |
| 10/12 | 39.81° | 10 inches |
| 12/12 | 45.00° | 12 inches |
This table helps answer common questions like "What is a roof pitch chart?" or "What angle is a 6/12 roof pitch?"
The maximum span for a 2x6 roof rafter (assuming 16-inch spacing and standard load) is approximately:
For longer spans, using 2x8 or 2x10 rafters is recommended. Always consult building codes for safety compliance.
The cost of roof framing depends on the materials, design complexity, and labor. On average:
Using our calculator can help estimate material requirements, reducing waste and saving money.
Our Roof Framing Calculator is the perfect tool for anyone planning a roofing project. Whether you’re building a small shed, a lean-to, or a full home, accurate rafter spacing, pitch angle, and span length are essential. This tool simplifies the calculations, improves accuracy, and speeds up your workflow.
By using our calculator, you no longer need to guess or manually draw roof pitch angles. Everything is calculated for you in seconds, giving you confidence in your project and ensuring building code compliance.
Yes, the calculator is ideal for shed, lean-to, and small structure roof designs.
A 4/12 to 6/12 pitch is considered ideal for most residential roofs offering a balance between water drainage and walkability.
It depends on the span and load. Common choices include 2x6, 2x8, and 2x10. The longer the span, the larger the rafter.
Most municipalities require a permit for structural work. Check your local building department for details.
Yes, our calculator includes an option to print or export your rafter plan and results.