This calculator is to be used as an estimating tool only.
Roof rafter size table.
For pitched roofs flat roofs and ceiling joists.
Input the rafter span on the flat eave overhang and pitch of the roof.
For example in the rafter span table below the highlighted cell in the 40 live load table indicates that 2 x 8 southern yellow pine joists that have a grade of 2 that are spaced 24 apart can have a maximum span of 10 feet 3 inches 10 3 if designing for a live load of 40 lbs ft 2.
Surveyors span tables for designing roof rafters.
It is always better to have a large rafter rather than be concerned with a sagging roof.
Our roof rafter calculator tools are handy for calculating the number of rafters needed rafter length calculator lineal feet of rafter board feed in ridge and sub facia and the total board feet in the roof.
Click the button to calculate the stock size needed for this job.