What is the formula to calculate the truss length?

The correct choice involves adding one to the quotient of the length in inches divided by the on-center spacing. This approach is essential for accurately determining the truss length because it accounts for the overall structure's requirements.

When calculating the truss length, it's crucial to recognize that simply dividing the total length by the on-center spacing gives you the number of intervals between the trusses. However, to find the total number of trusses needed along that length, one additional truss is necessary at the start or end of the span. Hence, the formula correctly reflects the need for this extra unit by adding one, ensuring that the final calculation includes all required trusses for structural integrity and design compliance.

This method addresses a common oversight in truss calculations where only the intervals are counted, leaving out the necessary truss that starts the first interval. By employing this formula, you can accurately plan truss layouts while ensuring the stability and strength of the constructed framework.