Truss Calculator

How to use this truss calculator

The calculator above takes five inputs: building span (the width of the building, outside-to-outside wall plate distance), roof pitch (rise per 12 of run), truss type, building length, and truss spacing. It returns truss height, chord lengths, truss count, and cost estimates. Most users get a usable estimate in under a minute.

1. Enter the building span. This is the outside-to-outside wall plate distance — the width the truss will need to span. Common residential spans are 24-32 feet for medium homes, 32-48 feet for larger homes, up to 60 feet for great rooms. The calculator handles spans from 12 to 80 feet.
2. Enter the roof pitch. Standard residential pitches are 4/12 to 12/12. Steeper pitches give more attic clearance and shed snow better; flatter pitches are cheaper and more modern in appearance.
3. Pick the truss type. Common (Fink/Howe) is the standard residential truss — cheapest and used in 80%+ of residential framing. Attic truss has a habitable space inside the truss (storage or finished attic). Scissor truss creates a vaulted ceiling below. Mono truss is a single-slope truss for shed roofs and porch roofs.
4. Enter the building length. This is the length perpendicular to the span — how far the trusses extend along the long axis of the building. Used to count the trusses needed at the chosen spacing.
5. Pick truss spacing. 24" on-center is the standard residential spacing. 16" on-center is used for heavier loads (steeper pitches with high snow loads, heavy roofing materials, longer spans).
6. Read the outputs. Truss height tells you how much attic space you have. Chord lengths tell you the rafter-equivalent dimensions. Truss count gives you the order quantity. Cost estimates set your budget expectation. For a real project, the fabricator quote will land within ±20% of these figures.

Truss vs. rafter — when each makes sense

Trusses and rafters both create roof structure, but they work very differently. Rafters are individual sticks of dimension lumber cut and assembled on-site by framers. Trusses are pre-engineered triangular structures fabricated off-site at a truss plant and delivered ready to install. The choice between them affects cost, schedule, and the resulting attic space.

Trusses are typically 15-30% cheaper than stick framing for the same project, because (a) they use shorter lumber pieces (the webs are 4-6 ft) more efficiently, (b) they install in 1-2 days vs. 4-7 days for stick framing, and (c) they require less skilled labour on-site. The downside is the engineered web pattern — most trusses fill the entire space inside, leaving little usable attic. Storage trusses or attic trusses solve this with a designed open space, but cost more.

Rafters (stick framing) are slower, more expensive, and require skilled framing carpenters — but produce a fully open attic space that can be finished as living area later. Stick framing also handles complex roofs (multi-pitch, irregular dormers, vaulted ceilings) better than trusses, where each truss profile is unique and the engineering cost compounds.

For typical residential single-family construction with a simple gable or hip roof and no attic-living plans, trusses win on cost and schedule. For complex roofs, attic conversions, vaulted-ceiling great rooms, or owner-builders who want flexibility during framing, stick rafters often win. The site's rafter length calculator covers stick-framing geometry; this page covers trusses.

Common truss types — Fink, Howe, scissor, attic, mono

Residential roof trusses come in several standard configurations, each suited to different applications. The five most common types account for nearly all U.S. residential framing.

Fink truss: the standard residential truss, recognizable by its W-shaped web pattern. Spans 24-50 feet typical, 4/12 to 12/12 pitch range, simple manufacturing, and the cheapest option. About 70% of U.S. residential trusses are Fink trusses. The W web pattern is structurally efficient — the lumber is loaded mostly in tension and compression with minimal bending.

Howe truss: an alternate web pattern with an N or M-shape inside, used for slightly heavier loads or longer spans than Fink. About 10-15% of residential trusses. Howe is more efficient for snow-load regions in the 50-foot+ span range; for shorter residential spans the cost difference is negligible.

Attic truss: a Fink-style truss with a designed habitable space in the upper interior. The bottom chord and the lower portion of the top chords define a room (typically 8-10 feet wide and 7-8 feet tall) suitable for storage or finished attic living space. An attic truss calculator returns the habitable dimensions in addition to the standard chord lengths. Cost premium: 50-100% above standard Fink for the same span.

Scissor truss: the bottom chord slopes upward toward the ridge, creating a vaulted ceiling in the room below. The vaulted ceiling typically has half the pitch of the roof above (a 12/12 roof with a 6/12 vault, for example). A scissor truss calculator returns the vault dimensions and clear-span height. Cost premium: 25-50% above standard Fink.

Mono truss: single-slope truss for shed roofs, lean-to additions, and porch roofs. Top chord on one side only; the other side is supported by an outside wall. Uses less lumber than a paired truss for the same coverage area. A mono truss calculator returns the single-slope geometry. Used in roughly 5% of residential trusses, mostly for additions and outbuildings.

Other less-common types include parallel-chord trusses (used for floor joists and flat ceilings — covered as truss joists in a different reference), gambrel trusses (barn-style two-pitch top chord), and queen-post or king-post trusses (architectural revival styles in custom homes).

Truss span and dimension reference

Standard residential trusses cover spans from 12 to 80 feet, with spans of 24 to 40 feet being the residential sweet spot. The roof truss dimensions for any given span depend on pitch and truss type — these roof truss measurements (height, chord lengths, web pattern) follow directly from the geometric formulas above. The roof trusses span chart below shows the truss height for common combinations of span and pitch — useful as a quick reference for planning attic clearance and exterior elevation.

For a 30 foot 4 12 truss dimensions question — total height 5 feet, top chord length about 15.8 feet per side, bottom chord 30 feet, web pattern 5 webs in a Fink configuration. For a 24-foot truss at 6/12: total height 6 feet, top chord 13.4 feet per side. For a 40-foot truss at 6/12: total height 10 feet, top chord 22.4 feet per side.

Truss spacing is typically 24" on-center for standard residential, 16" on-center for heavier loads. A truss spacing calculator confirms the count for a given building length: at 24" on-center, a 40-foot building uses 21 trusses (plus 1 end gable on each side = 23 total). At 16" on-center, the same 40-foot building uses 31 trusses (plus 2 end gables = 33 total). The denser spacing roughly doubles the cost — usually only worth it for high-snow regions or premium roofing materials.

A truss joist (also called I-joist or engineered joist when used for floors) is a different product entirely from a roof truss — the truss joist span chart and truss joist span tables references describe maximum allowable spans for engineered floor joists, not roof trusses. For roof truss span guidance, the table above is the relevant reference; for engineered floor joist spans, see the floor joist calculator on this site.

Truss cost — what to budget per truss and per house

Truss cost in 2026 ranges from $3-5 per linear foot of span for standard residential Fink trusses, fabricated and delivered. A 24-foot Fink truss costs $72-120 per truss; a 32-foot truss costs $96-160; a 40-foot truss costs $120-200. The truss price calculator above applies these per-linear-foot rates to your specific span; the truss cost calculator output assumes typical residential lumber grades and snow loads.

Premium truss types cost more. An attic truss at the same span runs $7-10 per linear foot — the 24-foot attic truss costs $168-240 per truss, almost double the standard Fink. A scissor truss runs $5-8 per linear foot ($120-192 for the 24-footer). A mono truss runs $4-6 per linear foot ($96-144 for the 24-footer).

Total truss cost for a typical house: a 28×40 foot house at 6/12 pitch with standard Fink trusses needs 21 trusses (24" on-center over the 40-foot length). At $4/lf × 28 ft = $112/truss × 21 = $2,352 for trusses alone. Add $400-600 for delivery and crane setup; figure $300-500 for incidental hardware (hangers, gable bracing, ridge ties). Total truss budget for the typical residential build: $3,100-3,500. The truss cost estimator above adds these typical extras to give you the realistic budget figure.

For an attic-truss version of the same house: 21 attic trusses × 28 ft × $8.50/lf = $4,998 in trusses alone. Add the same delivery and hardware: $5,700-6,100 total. The premium for attic-style adds $2,500-3,000 to the truss budget — and may add $5,000-15,000 to the total finish budget if you actually finish the attic space later.

Roof truss cost estimator queries that just want the per-truss rate: $3-5 per linear foot of span for standard residential Fink trusses, $5-8 for scissor, $7-10 for attic, $4-6 for mono — fabricated and delivered to the jobsite locally in U.S. markets in 2026. Multiply by your span and number of trusses for the total.

When trusses need engineer review and code compliance

Every residential roof truss in the United States must be designed by a licensed engineer and sealed with the engineer's stamp on the truss design drawing. This is not optional — it is required by the IRC (International Residential Code) Section R802.10 for any structural truss in residential construction. The engineering is typically done by the truss fabricator's in-house engineer (or a contracted engineer), not by the homeowner or general contractor.

The fabricator's truss design package includes: the truss profile drawing showing all dimensions, the lumber species and grade for each member, the metal connector plate sizes, the design loads (dead load, live load, snow load, wind), and the engineer's seal. The general contractor or homeowner provides this package to the local building inspector for permit review.

When the homeowner or contractor needs separate engineer review: when modifying trusses on-site (cutting webs, drilling for plumbing, adding loads), when a truss is damaged during installation, when changing the building geometry after trusses are ordered, or for unusual configurations not covered by the standard design package. Modifying a truss without engineer approval voids the warranty and creates liability — even small modifications (drilling a 3/4" hole through a top chord for an electrical run) can compromise the engineered design.

A truss member force calculator returns the load on each member of a truss — useful for engineering analysis but not a substitute for an actual engineer's sealed drawing. Similarly, a 2d truss calculator or 3d truss calculator returns geometric and structural analysis but cannot replace the engineering certification required by code.

Truss design software and tools

Professional truss design uses specialized engineering software, while homeowners and DIY framers often use simpler online calculators for planning. The two categories serve different purposes; mixing them up causes problems.

Professional fabricator software includes MiTek SAPPHIRE, Alpine InsiteFL, RoofTracker, and various proprietary systems used by major truss manufacturers. These integrate engineering analysis, lumber takeoff, plate design, and shop-drawing generation. The output is the engineer-sealed truss design package that satisfies IRC code requirements. Cost: $5,000-25,000+ in licensing for the fabricator. Homeowners cannot use these directly; you order the truss design through a fabricator who runs the software in-house.

Open-source and educational software for engineering students and curious DIYers includes the various 2D truss analysis tools available online — a truss simulator or truss solver that lets you build a truss virtually, apply loads, and see member forces. These are educational; they are not a substitute for an engineer's sealed design. Free truss calculator and truss solver free options serve this educational purpose. A truss analysis calculator returns the same kind of educational analysis.

Mobile and web tools for planning and budgeting include this calculator, the various roof truss design app options on mobile platforms (typically Android and iOS — search for "truss design" in the app stores), and timber truss design software targeted at small-shop builders. These are planning tools, not engineering certifications.

A 3d truss solver or 3d truss calculator runs the structural analysis in three dimensions, useful for complex truss geometries (irregular hip roofs, valley intersections, multi-pitch designs). 3D analysis is overkill for standard residential trusses; the fabricator software handles 3D as needed for unusual cases.

For most residential projects, the workflow is: use this calculator (or any free truss calculator) for budget planning → take the building plans to a truss fabricator → receive the engineered truss design package → submit to building department for permit. The DIY analysis tools are educational; the fabricator engineering is the actual deliverable that satisfies code.

How we sourced this content

Truss specifications and pricing follow accepted U.S. residential framing standards as documented in the IRC (International Residential Code) Section R802.10, the Truss Plate Institute (TPI) standards (TPI 1-2014 and current editions), and the Wood Truss Council of America (WTCA) educational materials. Cost figures reflect 2026 typical residential pricing from major U.S. truss fabricators (Builders FirstSource, US LBM, BMC, and regional manufacturers) at standard residential lumber grades and snow loads.

Recommendations are reviewed annually and updated whenever code or industry pricing changes materially. For specific projects, defer to your truss fabricator's engineering department for sealed design drawings and to your building department for permit-specific requirements. This calculator is a planning reference, not engineered design.