Select the priorities for the perks in the PRI column
Click Calculate
Play Fallout 4
To Do List:
Add Current Build to calculate forward
Correct some annoying CSS
Include Bobbleheads / You're Special
Some form of save feature / build sharing
Update Log 12/15/2015:
Added Random button which picks 35ish ranks of perks and calculates a build.
Added popup mouseover for perk ranks.
Adjusted the priority inputs to hopefully make it more clear that they can be changed.
Allowed perks to have their own priority.
Allowed the selection of a max rank in the perk.
Changed the sorting on the calculated levels to get a greater variety of perks earlier. The calculate will now sort every rank of the perks you have selected by the level and then sort them in the levels by priority.
Changed title in the special box to make it more clear that these are your intended starting special.