Construction

Roof Truss Calculator

Count roof trusses from length and spacing.

Building length

Truss spacing

Calculated Output

Trusses needed 13

Formula: trusses = length × 12 ÷ spacing + 1

Step-by-Step Breakdown

1. Values used:

2. Building length = 1

3. Truss spacing = 1

5. Trusses needed = 13

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The math behind it

trusses = building length (in) ÷ spacing + 1. 24 in on-center is common.

40 ft at 24 in → 21 trusses.

Gable ends?

Gable-end trusses may be a special type — count them in the total.