Roof truss geometry
Pick a king post, queen post or Fink truss, enter the span, the pitch, the overhang and the heel, and get every member's line length and angle with the truss drawn to match. Geometry only: it does not size lumber or plates, and a real truss comes with a stamped drawing.
Outside of wall to wall
Rise per foot of run
Advanced settings12" overhang · 0" heel
Level, past the wall
0 for a standard heel; more for a raised one
Top chord, Fink truss
174 7/16"top chord
Bottom chord
288"
Peak height
72"
Per truss
74.7 lin ft
Geometry, not engineering
This draws the truss and measures it. It does not size a single member or plate, and it cannot tell you whether a truss carries your roof: lumber grade, plate gauge, snow and wind load are a truss designer's job, and engineered trusses arrive with a stamped drawing that overrides anything here. Building your own? Ring your building department first — many will not pass a site-built truss without an engineer's stamp.
Members, one truss
Line lengths, panel point to panel point, the way a truss drawing dimensions them — not cut lengths. What comes off for the chord's depth and the joint is yours to lay out.
- A · Top chord × 2161" heel to peak plus a 13 7/16" tail — cut from 16 ft stock
- 174 7/16"
- B · Bottom chordOutside of wall to outside of wall
- 288"
- C · Short web × 256.3° from the bottom chord
- 43 1/4"
- D · Long web × 256.3° from the bottom chord
- 86 9/16"
Cut angles
- Top chord at the peakPlumb cut, saw setting off square
- 26.6°
- Top chord on the bottom chordThe angle between the two chords at the heel
- 26.6°
- Peak heightBottom of the bottom chord to the top of the peak, on a 24 ft span
- 72"
Top chord peak cut, at true size
Print at 100%, check the ruler, and set a bevel gauge from it — stock on the baseline, blade on the second line — to mark the plumb cut on every top chord the same.
Put a tape on the printed ruler. If it does not read exactly 6 inches, the print was scaled — set the print dialog to 100% or “Actual size” and print it again. Do not cut wood from a template that failed this.
The baseline is the chord's top edge; the second line is plumb at the peak.
Worked example: a 24 ft Fink (W) truss at 6:12
A 24 ft Fink (W) truss at 6:12 peaks 72" above its bottom chord. Each top chord is 161" from heel to peak along its top edge, plus 13 7/16" of tail for a 12" overhang: 174 7/16" in all.
The webs are 2 short webs at 43 1/4", 56.3° from the bottom chord, and 2 long webs at 86 9/16", 56.3° from the bottom chord. One truss is 74.7 linear feet of line length.
The peak plumb cut is 26.6° off square. These are line lengths for the geometry only; the lumber and plates are a truss designer's to size.
- Top chord
- 174 7/16"
- Bottom chord
- 288"
- Short web × 2
- 43 1/4"
- Long web × 2
- 86 9/16"
- Peak height
- 72"
These are the figures the calculator above opens on. Change any field and it works the same problem for your numbers.
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About roof trusses
- What is the difference between a king post, queen post and Fink truss?
- The webs. A king post truss has one vertical from the middle of the bottom chord to the peak, which suits short spans like a shed. A queen post has two verticals at the third points with a straining beam across their tops, leaving the middle open. A Fink has four webs in a W, from the bottom chord's third points to the middle of each top chord and to the peak — it is the commonest light-frame roof truss, because it breaks each top chord into two short spans.
- How long is the top chord of a 24 ft truss at 6/12?
- 161" from the heel to the peak along its top edge, plus 13 7/16" for a 12" overhang: 174 7/16" in all, which is the same line length as a common rafter on that roof. The peak stands 72" above the bottom of the bottom chord. Those are line lengths; the cut length depends on how the joints are made.
- Can this calculator size truss lumber or gusset plates?
- No, and nothing that only knows the geometry can. Whether a truss carries a roof depends on the lumber grade of every member, the plates, the spacing, and the snow and wind load where you are building. Engineered trusses come with a stamped drawing that settles all of it. If you are building your own, ring your building department first — many will not pass a site-built truss without an engineer's stamp.
- What is a raised heel truss?
- One whose top chord is lifted above the bottom chord at the wall, with a short vertical closing the end. The point is room for full-depth attic insulation over the wall plate, where a standard heel pinches it to a few inches. The whole roof goes up by the heel: a 24' truss at 6/12 peaks 72" above its bottom chord with a standard heel and 84" with a 12" one, so check the ridge height against anything with a height limit.
You might also need
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- Roof pitch calculatorRise and run, x/12, degrees or a rise over a span turned into all the others, with the slope multiplier and the plumb and seat cuts.
- Pole barn calculatorPosts, trusses, girts and purlins at the spacings you choose, with the roof and wall steel for a post-frame building.