I've just added a new calculator to blocklayer.com that works out post and panel spacings (fences) with the panels between the posts. (The other fence calculator is for rails attached to one side of the posts)


https://www.blocklayer.com/post-panel.aspx


With this one, you can choose end post options - Posts Both Ends - Post One End Only - No End Posts - and panel options to fit total length - Cut Last Panel - Cut Both End Panels - Adjust all Panels Equal.
It works out all spacings and draws an elevation to scale with everything marked, and options for paling gaps to fit the panels evenly, or just full panels (no palings)
You can drag the sliders to animate and scale the diagram so you can see what happens when you change things.
Please let me know if it needs additions, edits or fixing in any way.

post-panel.jpg