About the king post roof truss
A king post truss is the simplest triangulated truss: two rafters, one tie beam and a single vertical post from the tie beam to the ridge. It is modeled here with the gable geometry because the outer shape is the same.
When to choose it
It suits short spans such as sheds, porches, small garages and timber-frame details. For wider spans the member sizes grow quickly and a multi-web truss becomes more efficient.
How to use this calculator
- Enter the building span and the length along the ridge.
- Pick the pitch (or switch to an exact angle) and set the eave overhang.
- Choose spacing, material, snow and wind loads. Results update as you type.
Use the rafter length and rise results to cut the two top chords and the central post.
Practical tips
Joints matter more than member length in a king post truss. Use proper connector plates or well-fitted timber joints. See how to build a truss for assembly basics.
Need a different figure? Try the span calculator, the cost calculator or compare options on the all truss types page.