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MaterialCalc — Roof Truss Count & Cost Calculator

Estimate prepared 09/01/2026. Estimates only; verify against your plans before ordering.

Roof Truss Count & Cost Calculator

The ridge direction — trusses are spaced along this.

The truss span. Price rises steeply with this.

Usually two, and they cost more than a common truss.

%

Trusses are made to order, so this is small.

Result

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Truss count is straightforward — building length divided by spacing, plus one. What makes truss roofs expensive is what surrounds that number: gable ends cost more than commons, span drives the unit price steeply, and above about 24 ft you are hiring a crane. This counts the trusses and prices the whole day.

Assumptions used

These are the numbers behind the result. Where one of them is soft, the cost range widens rather than pretending to a precision the data does not have.

Roof truss spacing
24 in o.c.

International Residential Code (2021) — Published product data, checked 09/01/2026

Prices verified 09/01/2026 (US national average, big-box retail shelf price and regional ready-mix quotes). Regional adjustment: Blended from RSMeans city cost index bands and BLS construction wage differentials.

The formula

Trusses = (building length ÷ spacing) + 1. Subtract the gable end trusses from that to get the commons, since gable ends occupy end positions. Bracing = building length × 3 rows, in 16 ft lengths. Hurricane ties: two per truss, one at each bearing.

Worked examples

40x28 house roof at 24 in o.c.

Building length: 40 Building width: 28 Truss spacing: 24 Gable end trusses: 2 Waste: 2

21 trusses — 19 commons and 2 gable ends. At 28 ft of span this is a crane day, and the crane is a meaningful share of the cost.

24x20 garage at 24 in o.c.

Building length: 24 Building width: 20 Truss spacing: 24 Gable end trusses: 2 Waste: 2

13 trusses over a 20 ft span. Short enough that a crew can set them by hand, which takes the crane out of the budget.

60x32 barn at 16 in o.c.

Building length: 60 Building width: 32 Truss spacing: 16 Gable end trusses: 2 Waste: 2

47 trusses. Sixteen inch spacing over a 32 ft span is a lot of truss — worth asking the supplier whether a heavier truss at 24 in is cheaper overall.

Choosing materials

  • Truss price rises steeply with span, not linearly. A 28 ft truss costs far more than twice a 14 ft one, because the web configuration and the chord sizes both change.
  • Gable end trusses are built with vertical studs at 16 in for sheathing rather than a webbed configuration. They cost roughly 40% more than a common truss and you need one at each end.
  • Order six to eight weeks out. Trusses are made to order for your exact span, pitch and bearing conditions, and lead time is the usual reason a roof sits open.
  • Temporary and permanent bracing is not optional. Trusses are strong in plane and floppy out of it — an unbraced set falls like dominoes, and it happens on real sites every year.
  • Check the delivery access before ordering. A truss trailer needs room to get in and room to unload, and a set stacked in the wrong place has to be moved by hand.

Common questions

How many roof trusses do I need?

Divide the building length by the spacing and add one. A 40 ft building at 24 in on center needs 21 trusses, two of which are gable ends. At 16 in on center the same building needs 31.

How much does a roof truss cost?

A common residential truss runs roughly $110 to $250 depending on span, pitch and lumber prices. Gable end trusses cost about 40% more. A 40x28 roof is typically $2,800 to $5,000 in trusses alone, before the crane.

Are trusses cheaper than stick framing?

Usually yes, once labor is counted. Trusses are engineered, arrive ready to set, and a roof goes on in a day rather than a week. Stick framing wins where you want usable attic space or a complicated roof that trusses cannot easily produce.

Do I need a crane to set trusses?

Above about 24 ft of span, effectively yes. Longer trusses are heavy and unstable out of plane, and hand-setting them is both slow and genuinely dangerous. A crane day usually costs less than the extra labor it displaces.

What spacing should roof trusses be?

Twenty-four inches on center is standard for residential trusses and is what most are designed for. Sixteen inches is used for heavy snow loads or where the roof carries unusual point loads, and it needs a third more trusses.

Can I cut or modify a truss?

No. Every member in a truss is engineered and cutting any of them voids the design. If you need to alter one — for a chimney, a skylight, an attic hatch — that has to be designed by the truss engineer before it is built.

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