Ramp into the bottom of a coop?

[JTofSD]

Hi everyone,
I am building a chicken coop tractor. The ramp is designed to allow access into the coop from the bottom, not the side of the coop. My question for all of you is, at the top of the ramp, how much space do chickens need to have to be able to turn and get into the coop? A ramp into the side of the coop would allow the chickens to walk right in, but a ramp coming up from below means that the chickens must turn at the top of the ramp. I hope that makes sense.
I found these images on a different thread here, but it is like 9 years old. I post them to help you understand my question. My ramp is much more shallow of an angle.

 

[sourland]

I would guess slightly larger than the lateral size of the bird. It would vary from breed to breed so 'bigger is better'.

 

[Dinogrrl]

Not that much room. The top of my ramp came within a few inches of the wall of the coop, one side of the ramp was maybe 6 inches from the other wall, and the remaining two sides were several feet away from anything. The chickens rarely walked up the whole ramp though, and would just hop from the ramp to wherever they wanted inside the coop.

My chickens are always hopping up on branches and roost bars that are only like 1-2 inches in diameter and if they don't have enough room for their entire fluffy bodies they can scoot around pretty quickly and not lose their balance. They figured out the under-coop ramp pretty easily.