Every nozzle manufacturer has the PR of their nozzles on their website these days…
Here are the nozzles I have in my yard. Shows GPM, GPH, and…would ya look at that! Precipitation in in/hr!
I’m not going to argue that PR calculation doesn’t require square footage, but the manufacturer has done it for you based on the radius of the nozzles reach (sq ft area), GMP, and sprinkler overlap (assuming a relatively well executed irrigation system).