Gambrel Roof Framing Geometry
Rafter Calculator & PDF Plans
USD 1.99 · Designed for iPad. Not verified for macOS.
Gambrel Roof Framing Geometry is the professional tool for calculating every dimension, angle, and cut you need to frame a gambrel (barn-style) roof — right from your iPhone or iPad.
Enter your wall width, rafter depth, roof angles, and overhang, and instantly get precise measurements for lower rafters, upper rafters, birdsmouth cuts, joint geometry, gusset plates, purlin offsets, ridge offsets, and total roof area. Every value updates in real time as you adjust parameters.
INTERACTIVE DIAGRAMS
• Full cross-section profile of the complete gambrel roof
• Detailed lower rafter diagram with birdsmouth seat, plumb cut, and all angles
• Detailed upper rafter diagram with tail cut and joint geometry
• Top gusset and mid gusset dimension diagrams
• Pinch to zoom and pan on every diagram for close-up detail
COMPLETE RESULTS TABLE
All computed values organized in collapsible professional sections:
• Overall dimensions — total width, height, peak inner height
• Lower and upper rafter — length, rise, run, effective length, pitch ratio
• Joint geometry — joint angle, half-joint angle, offset, position
• Rafter cuts — plumb cuts, tail cuts with exact measurements
• Purlin and ridge offsets — half offset, cos/sin components
• Birdsmouth — seat width, height offset, max seat, cut length
• Gusset plates — angle, base, slope height, slope length
• Roof area — total area calculated from roof length
IMPERIAL & METRIC UNITS
Switch instantly between imperial (feet-inches-fractions) and metric (millimeters) input modes. Imperial mode uses traditional picker controls with fractions down to 1/16". Metric mode provides direct text entry for fast input. Results display in your chosen system.
SEMI-CIRCLE MODE
Constrain the gambrel profile to fit inside a perfect semicircle with one tap. The calculator automatically derives the upper roof angle and lower rafter length from your lower roof angle.
PDF EXPORT
Generate a professional multi-page PDF containing all diagrams and the complete results table. Share via email, AirDrop, save to Files, or print directly — perfect for job sites, permit applications, and client presentations.
DISPLAY OPTIONS
• Color fill or outline-only diagrams
• Show/hide dimension labels
• Add a person silhouette for visual scale reference
• Adjustable person height for accurate perspective
BUILT FOR PROFESSIONALS
Whether you are a carpenter, timber framer, builder, architect, or serious DIYer, this calculator eliminates manual trigonometry and gives you every measurement needed to lay out and cut gambrel roof trusses with confidence.
All calculations are geometric. Always verify results against local building codes and engineering requirements for your specific project.
Ratings & Reviews
- This app has not received enough ratings or reviews to display an overview.
The developer, Vladislav Zhirnov, indicated that the app’s privacy practices may include handling of data as described below. For more information, see the developer’s privacy policy .
Data Not Collected
The developer does not collect any data from this app.
Accessibility
The developer has not yet indicated which accessibility features this app supports. Learn More
Information
- Seller
- Vladislav Zhirnov
- Size
- 3.5 MB
- Category
- Utilities
- Compatibility
Requires iOS 17.6 or later.
- iPhone
Requires iOS 17.6 or later. - iPad
Requires iPadOS 17.6 or later. - Mac
Requires macOS 14.6 or later and a Mac with Apple M1 chip or later. - Apple Vision
Requires visionOS 1.3 or later.
- iPhone
- Languages
English and 31 more
- English, Arabic, Croatian, Czech, Danish, Dutch, Finnish, French, German, Greek, Hebrew, Hindi, Hungarian, Indonesian, Italian, Japanese, Korean, Malay, Norwegian Bokmål, Polish, Portuguese, Romanian, Russian, Simplified Chinese, Slovak, Spanish, Swedish, Thai, Traditional Chinese, Turkish, Ukrainian, Vietnamese
- Age Rating
4+
- 4+
- Copyright
- © zhirnov.zsystems
