For pitched roofs flat roofs and ceiling joists.
Roof rafter size table.
It is always better to have a large rafter rather than be concerned with a sagging roof.
This calculator is to be used as an estimating tool only.
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.
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.
Input the rafter span on the flat eave overhang and pitch of the roof.
Rise and run means that a 6 12 pitch roof has 6 of rise vertical for each foot of run horizontal.
If your project had a rafter length of 8 or less a safe and strong method is to use 2x8 framed 16 on center.