About Roof Truss Calculator

Why this site exists

Truss geometry is not complicated. It is Pythagoras, a slope factor and a bit of bookkeeping. But the numbers you need are scattered across span tables, supplier PDFs and forum posts, and none of them tell you what happens when you change the pitch by two inches.

So we built the thing we wanted: enter a span, watch the truss draw itself, and read every derived number at once, chord lengths, cut angles, board feet, weight, bearing reactions and package cost. Change an input and the whole chain recomputes instantly.

How the calculations work

Each calculator builds your truss as a coordinate model first: bearing points, heel points, the peak, break points and every web node, positioned from your span, pitch, heel height and overhang. The web pattern is chosen from the span, king post, queen post, fink or double fink, following standard practice.

Every quantity then comes from measuring that model. Member lengths give lineal footage, which gives board feet and weight. Span and spacing give tributary area, which turns your psf loads into pounds per lineal foot and bearing reactions. Truss count and unit price give a package cost. Because it all derives from one geometric model, the numbers are internally consistent, the take-off always matches the drawing.

What we are not

We are not a substitute for a structural engineer, and we will not pretend otherwise. Our calculators do not size individual members from actual forces, design connector plates, check load combinations, analyse wind uplift or model snow drift. Those require a real engineered design, and any truss you buy from a fabricator arrives with one included.

What we do give you is the ability to plan, budget, compare options and arrive at a supplier conversation already knowing what you need. That is a genuinely useful thing to be, and it is what we try to be well. We wrote a full piece on where the line between a calculator and an engineer sits .

Corrections welcome

If you find a figure that looks wrong, a table that has drifted from current market rates, or a calculation that does not match your supplier's drawing, tell us. We would rather fix it than defend it. The contact page reaches us directly at hello@rooftrusscalculator.online.