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Use our roof truss span calculator to find roof truss span from rise and pitch. Get fast results with a simple roof span formula.
| Formula | Meaning |
|---|---|
| Run = Rise × 12 ÷ Pitch | Horizontal distance from bearing point to ridge |
| Span = 2 × Run = 24 × Rise ÷ Pitch | Total horizontal truss span for a symmetrical gable roof |
A roof truss span tells you how wide a truss can reach. It runs from one wall support to the other. We made this roof truss span calculator so you can find the span fast.
It uses simple roof math. It works when you know the rise and roof pitch. It helps with early roof plans. It does not check if a truss is safe for a real job. A truss maker must check the loads and the site. Wood trusses are engineered parts made for set loads and uses.
For a gable roof, both sides match. So, the full span is twice the run.
Span = 2 × Run
If you know rise and pitch, use:
Run = Rise × 12 ÷ Pitch
So:
Span = 24 × Rise ÷ Pitch
Pitch means roof rise for each 12 units of run. The same math works in feet or inches. Keep the units the same.
Say the rise is 6 ft. The roof pitch is 6/12.
First, find the run.
Run = 6 × 12 ÷ 6
Run = 12 ft
Now find the span.
Span = 2 × 12
Span = 24 ft
So, the roof truss span is 24 ft.
This helps with a common question: what size truss for 24 foot span? The span alone does not pick the truss size. Load, wood grade, truss depth, spacing, and support also matter. Truss drawings also set items such as spacing, bearing points, and bracing.
A roof truss is an engineered frame. Its parts form strong triangles. Wood trusses often use 2×4 or 2×6 lumber. The right truss depends on the job and load.
Do not use a roof truss span chart as a final design. A roof truss span chart, wood roof truss span chart, or roof truss span table can help with early checks. Final design needs the right loads and code rules. Span tables use set load and support rules, so they are not one-size-fits-all.
The same idea applies to a wood truss span calculator, roof joist span calculator, and roof truss spacing calculator. Each tool has a set use. A floor truss has a different job from a roof truss.
You may also see truss height to span ratio and truss depth to span ratio. These terms show truss shape. They do not replace a full design check.
The roof truss span calculator gives you a fast span result. The key rule is simple: span equals twice the run. With rise and pitch, use span equals 24 times rise divided by pitch.
It helps with plans, checks, and early cost work. For a real build, get the final truss design from a qualified truss maker or engineer.
There is no one safe span for every truss. Load, shape, wood, spacing, and support all matter. Some large wood roof systems span 30 to 50 ft. That does not mean every truss can do so.
Cost can vary a lot. It depends on wood, depth, load, pitch, shipping, and local rates. Get a local quote for a true price.
A 24 ft span does not set one truss size. The design must also use load, spacing, pitch, wood, and support details.
A 2×4 label alone does not set the span. The full truss design controls span and strength.
You can use it for span math. It is not a full roof truss design calculator. It does not check loads or member strength.
Yes, if the tool accepts metric input. Keep the rise and run units the same.
Yes, many guides and tables exist. Use them for reference. Do not use them as a final design.
A basic roof truss span calculator can be free. Paid tools may offer deeper design checks.