local committee
PHRF ratings depend on local conditions, such as average wind strength, and are calculated by local committees. Most PHRF committees maintain websites that list the base ratings of various boats for that area. Your boat will ultimately deviate from the base rating due to the types of sails you've had built, whether or not you use a spinnaker, the type of propeller you run, et cetera. Ultimately, there is no substitute for paying application fee, usually somewhere in the $25-$35 range, and having your boat rated. That said, you can probably get on Google, type in "PHRF" and the name of your state/region, and find a base rating.