TryBuildCalcMono Truss Calculator (Single-Slope Truss)
Size mono trusses instantly.
🕒 Last updated: September 4, 2026
Inputs
ℹ️Informational/geometric only — the actual web layout is engineered by the truss designer regardless of the type selected here. Mono is a single-slope truss with no ridge.
ℹ️Outside wall to outside wall — trusses clear-span the full width, unlike stick-framed rafters.
ℹ️The length running along the ridge — determines the truss count.
ℹ️Rise per 12 inches of run — a 6/12 roof rises 6 inches for every 12 inches of horizontal run.
ℹ️Horizontal projection of the truss tail past the outer wall face, before any fascia trim.
ℹ️A raised (energy) heel gives full-depth insulation clearance at the wall line, common in modern energy-code-driven construction.
Waste
ℹ️Accounts for damaged pieces and layout adjustments on common trusses — 10% is a common estimating default.
Cost
Total Trusses Needed
13
13 common (+10% waste)
Overall Truss Height
3.50 ft
42" from bearing to ridge peak
Truss Geometry
Type: Mono (single-slope)
Pitch: 3/12 (14.04° from horizontal)
Run: 168" (14.00 ft)
Rise: 42" (3.50 ft)
Top chord length: 173.17"
Overhang tail: 12.37" (12" horizontal overhang)
Overall height (bearing to ridge): 42"
Truss Count
Spacing: 24" O.C. over 20 ft
Common trusses before waste: 11
Total with 10% waste: 13
Gable End Trusses
Not applicable to a mono/single-slope roof.
Truss-to-Wall Connectors
Count: 26
One hurricane tie/truss anchor per bearing point (2 per common truss) — confirm rating against local wind/seismic requirements.
Assumptions Used
Standard US light-frame prefabricated wood roof trusses, clear-spanning the full building width. Truss count uses the same on-center spacing formula as wall studs, rafters, and floor joists. Geometry (run, rise, chord length, overhang, overall height) is direct trigonometry from your entered span and pitch — not a code-table lookup, so it applies regardless of code edition. This calculator does not design trusses — real trusses are engineered components with member sizes, web layout, and metal connector plates sized by a truss designer using manufacturer design software, then fabricated to a stamped drawing; this is a quantity and geometry takeoff only. Gable end trusses (when included) are a fixed count of 2, not subject to the waste factor. Truss-to-wall connector count assumes 2 bearing points per common truss and does not include gable end truss fastening (typically toe-nailed/strapped along the gable wall, not a fixed per-truss count). Permanent and temporary bracing — one of the most safety-critical parts of truss installation — must follow the truss designer's own drawings and the industry-standard BCSI guide (SBCA/TPI), not this calculator.
Bill of Materials
Main material: 13 pcs + recommended tools
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Bill of Materials
Main material: 13 pcs + recommended tools
Computed items reflect your entered span, length, and spacing; consumables below are general recommendations — actual needs vary by product, wind/seismic zone, and site conditions.
For Your Job
Roof Trusses
Truss-to-Wall Connectors
General Tools & Consumables
Truss-to-wall connectors (hurricane ties/anchors)
Permanent bracing lumber
Temporary erection bracing lumber
Gable end L-brackets/stiffeners
Roof sheathing (OSB/plywood)
Framing nailer or hammer
Crane or forklift (for lifting trusses into place)
Tape measure
Chalk line
4 ft level
Safety harness & fall protection
Diagram simplified for clarity (not to scale) — actual web layout is set by the truss designer's engineered drawing.
Looking for the verification checklist, reference tables, tips, or common mistakes?See the complete Roof Truss Calculator.
Mono (single-slope) truss sizing
A mono truss has a single continuous slope from a low wall to a high wall, like a shed roof — common for additions, porches, and lean-to structures — and uses the full building span as its run, with no ridge or gable end trusses.
This page defaults to a 14 ft span shed-style roof — edit the inputs above to match your actual structure.
Roof Truss Calculator Formula: How Is It Determined?
Truss geometry, truss count, gable end trusses, and connector hardware, calculated separately and combined into a material takeoff.
Step 1 — Truss Geometry
Run = Common/Scissor/Attic: Span ÷ 2 | Mono: full Span
Angle = arctan(Top Pitch ÷ 12)
Rise = Run × (Top Pitch ÷ 12)
Top Chord Length = Run ÷ cos(Angle)
Overall Height = Heel Height + Rise
This is direct trigonometry applied to your entered span and pitch — a Pythagorean relationship between run and rise, not a code-table lookup, so it applies regardless of code edition. For a scissor truss, the same formula is applied a second time using the bottom chord pitch, and the difference in rise gives the vaulted ceiling height.
Step 2 — Truss Count & Gable Ends
Common Trusses (before waste) = ceil((Building Length in inches) ÷ Spacing) + 1
Total Common Trusses = ceil(Common Trusses before waste × (1 + Waste Factor ÷ 100))
Gable End Trusses = 2 (non-mono roofs, when included) — no waste factor applied
Truss count uses the same on-center spacing formula as field studs, rafters, and floor joists. Gable end trusses are a fixed count (one per gable end), not a spacing-formula piece count.
Step 3 — Truss-to-Wall Connectors
Connectors = Total Common Trusses × 2 (both bearing points)
Each common truss typically bears on the wall at two points, each commonly needing a rated connector (hurricane tie or truss anchor) resisting wind/seismic uplift. Gable end truss fastening (typically toe-nailed/strapped along the wall) isn't included in this count.
Worked Example
This example walks through your current inputs above, using the same steps as the Formula section.
Input Values Used
| Input | Value | Why it is used |
|---|---|---|
| Truss type / span | mono / 14 ft | Sets whether run is half or full span |
| Pitch | 3/12 (14.04°) | Sets rise, height, and chord length |
| Spacing / length | 24" O.C. / 20 ft | Sets the truss count |
Step 1 — Truss Geometry
| Calculation | Result |
|---|---|
| Run | 168" |
| Rise | 42" |
| Top chord length | 173.17" |
| Overhang tail | 12.37" |
| Overall height (bearing to ridge) | 42" |
Step 2 & 3 — Truss Count, Gable Ends & Connectors
| Calculation | Result |
|---|---|
| Common trusses before waste | 11 |
| Total common trusses (with 10% waste) | 13 |
| Truss-to-wall connectors | 26 |
Therefore, this 14 ft span, 3/12 pitch roof needs approximately 13 trusses total (13 common) and 26 connectors.
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Disclaimer: This calculator provides approximate results for planning and estimation purposes only. Actual requirements may vary based on site conditions, materials, workmanship, and local building regulations. Always consult a qualified engineer, architect, or construction professional before making final decisions.