I need help - first time builder

8 x 12 shed - need to know the height of ridge pole and length. I know on a 4/12 pitch it is 4 inch rise for 12 inch length, does this include the overhang. I would like to have about 8" overhang.

Thanks

Assuming that the roof will be orientated the 12 foot length. Assuming that the rafters will be 2x4. Assuming that the bird's mouth of the rafters will be cut to approximately 1/2 the width of the 2x4 rafter. The location of the ridge bean will be;
8'/2 = 4' or 48"
Assuming that the bird's mouth is cut to the approximate center of the rafter or 2", the final height of the ridge beam (top edge) will be 4" times 4' plus 2" or 18" above the top plate.

Length of rafter will be
A squared plus B squared = C squared.
18 X 18 + 48 X 48 = 2628
square root of 2628 = 51.26"

Length of rafter = 51.26 plus 8" over hang would be 59.26".

Assuming a 2x6 (5.5") ridge bean
Cut two studs 12.5" long and nail to center of end top wall plates. Attach ridge bean on top of studs using "L" brackets. Temporarily tack a 2x4 (flat) to top of ridge beam. Place a 2x4 rafter on the 2x4 (on the ridge beam) and the wall. Using a level, mark a plumb line at the ridge beam, the outside of the wall and 8" from the wall. Using a square mark the seat cut for the bird's mouth in the center of the wall line.

Cut to length and cut out the bird's mouth. Check the fit and use as a pattern for cutting the remaining rafters.

If you are installing a fascia board on the ends of the rafters, subtract 3/4" from length of rafter. Also subtract any amount you want the roof sheathing to over hang the end rafters or fascia board.