Is there a way to calculate a tractor's front PTO power?
The answer is unfortunately not as straight forward as the question would appear. Yes, there is a way to calculate the horsepower for any given PTO location however you would have to know a great many more things that just the Gross or Net HP of the machine such as gear reductions through the system to the take off point, friction loss due to contact.....
The great thing is that with a tractor the manufacture will list the Gross HP (measured at the flywheel) and Net HP (actual power available for use). The Net will have a drawbar rating and a PTO rating the latter generally being the higher of the two. So to find your front PTO rate, either look to the manual for the machine or call the manufacture for to get a spec sheet listing, or you may be able to utilize tractor data.net they list a large number of models on their site.