Gable Roof Truss Calculator
The gable roof — two equal slopes meeting at a central ridge — is the most common and most cost-effective residential truss shape. This gable roof truss design calculator takes your span, pitch, and spacing and instantly returns rafter length, ridge height, roof angle, roof area, and an estimated material cost.
Size Your Gable Roof Truss
Enter your building specifications below. Results and the roof diagram update live as you type.
Live Roof Diagram
Results
Estimate Your Project Budget
Automatically calculated from your inputs above in the calculator.
Estimates only. Actual costs vary by region, supplier, and site conditions.
Why Gable Trusses Are the Default Choice
A gable truss is a simple triangle: two top chords meeting at a ridge point, a bottom chord spanning the full width, and web members bracing the interior. Because the geometry is straightforward, gable trusses are the fastest to engineer, the cheapest to manufacture, and the easiest to install of any common truss type.
Gable roofs shed water and snow efficiently and work with almost any pitch from a low 2/12 slope up to a steep 12/12. The trade-off is wind performance — the flat gable ends can catch more wind uplift than a hip roof, so wind load and bracing matter more in storm-prone regions.
Use the calculator above to size a gable truss for your project, then check the Hip and Gambrel calculators if your design needs different wind performance or interior loft space.
Frequently Asked Questions
How to calculate roof truss size?
Measure the building span (wall-to-wall width) and choose the roof pitch. Truss size is set by the top-chord length (from span & pitch), the overall rise, and the required load. Enter span, pitch and load into the calculator and it returns member lengths, height and quantity.
How far can 2x4 trusses span?
Engineered 2x4 trusses can span up to about 30–40 ft in light-load residential roofs because the web members carry the load, not the chord alone. A single unsupported 2x4 rafter spans far less. Always confirm with an engineered, stamped truss design.
Simple truss calculator
Enter span, pitch and spacing for a fast, simple result — ideal for quick estimates before ordering.