Roof Truss Calculator
Accurately sizing roof trusses is essential for structural integrity and material ordering. This calculator determines truss height, rafter length, the number of trusses needed for your building, and the total linear feet of lumber required based on span, roof pitch, and truss type.
Roof truss geometry is driven by two primary measurements: the building span and the roof pitch. The truss height equals half the span multiplied by the pitch ratio (pitch/12). The rafter length is the hypotenuse of the triangle formed by the half-span and the truss height.
Common residential truss types include the king post (simplest, best for spans under 20 feet), queen post (good for spans up to 30 feet), and fink or W-truss (the most common residential type, efficient for spans up to 40 feet). Longer spans require engineered trusses.
Standard truss spacing is 24 inches on-center for most residential roofs, though 16-inch spacing is used for heavier loads such as tile roofing or areas with significant snow loads. Always consult a structural engineer for spans exceeding 40 feet or unusual loading conditions.