What this calculator does
Roof truss count works out number of roof trusses for a building length at a chosen on-centre spacing. Enter your own figures above and the answer updates as you type: nothing is fixed in the code, so the result reflects exactly the numbers you supply.
The formula this calculator evaluates is printed under the tool and explained below, so you can check the working by hand or reuse it in a spreadsheet.
The formula
FormulaTrusses = ⌈building length × 12 / on-centre spacing (in)⌉ + 1
The inputs explained
| Field | What to enter |
|---|---|
| Building length (m) | A number, measured in m. Starts at 12. |
| On-centre spacing | Choose from 16 in, 24 in, 610 mm. |
| Spacing unit | Choose from Inches, Millimetres. |
Worked examples
Every figure in the tables below is produced by this page’s own calculator at build time, so the numbers and the tool always agree. Select any row to load that scenario.
How the answer changes with building length
Every other input is held at the calculator’s starting values while building length varies. Select any row to load that scenario into the calculator.