Garage Roof Truss Calculator
Garages, barns, and shops typically need wider clear spans than a house, since there are no interior load-bearing walls to break up the truss. This garage roof truss calculator sizes wide-span gable trusses and returns rafter length, roof height, area, quantity, and material cost.
Size Your Garage or Barn 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.
How Big Can Garage Roof Trusses Be?
Because a detached garage or barn usually has clear space underneath with no interior walls, the trusses must span the full building width unsupported. Residential garage trusses commonly span 20–30 ft, while pole-barn and agricultural buildings can push well beyond 40 ft with engineered, deeper trusses.
What size should roof trusses be for a garage? That depends on span, spacing, snow load, and roof pitch — a wider span or heavier snow load calls for deeper chords, tighter web bracing, or closer truss spacing (12"–16" on-center instead of 24").
Use the calculator above with your garage or barn's actual span and expected snow/wind load, then compare 16" and 24" spacing to see the trade-off between truss count and per-truss size.
Frequently Asked Questions
How big can roof trusses be?
Residential garage trusses commonly span 20–30 ft, while engineered pole-barn and agricultural trusses can span well beyond 40 ft. Maximum span depends on chord size, web bracing, spacing, and load — always confirm with a stamped engineered design for wide spans.
What size should roof trusses be?
Truss size depends on span, spacing, pitch, and load. Wider spans or heavier snow/wind loads need deeper chords or closer on-center spacing; use the calculator to compare options for your building.
Barn roof truss calculator
Use the Gambrel calculator for classic loft-style barns, or this Garage/Barn calculator for simple wide-span gable barn roofs.