Campendium users will often tell you what site rigs will fit in boondocking sites for those listed. There is the option in Campendium to ask a question and it is often responded to.
Also, Freecampsites.net listings have great information and often list this info.
On Google Maps, there is an option to measure an area and that's been very helpful to determine road or back in area sizes.
Measure distance between points
On your computer, open Google Maps. ...
Right-click on your starting point.
Choose Measure distance.
Click anywhere on the map to create a path to measure. ...
Optional: Drag a point or path to move it, or click a point to remove it.
