Unfortunately I do not know of a calculator.
What are you trying to achieve? I'm having trouble visualizing it.
Are the eaves going to dump water inside the hoop coop? That could be a problem in most climates.
Two possible ways to work without exact numbers:
How wide is it going to be? Working with a 16 foot cattle panel, and looking at the images above, any width over about 10 feet will make the top height less than 5 feet.
For heights over 5 feet, you could pretend the top is as wide as the bottom of the hoop area. That should give more clearance than you need, but depending on how precise you
One way to get exact numbers: bend the cattle panel and measure. This can be easier if you stand the cattle panel on its edge (so it looks like a curved fence instead of a hoop coop), and use something straight to help you measure (maybe put the bottom of the arch along one edge of a driveway or one wall of a building, then measure out 5 feet from that on each side, then measure across the arch of the cattle panel at that point.)