brianogilvie 

On a closed loop course, 50 feet per mile ascending also involves 50 feet per mile descending. Those are both averages; obviously some sections of the course will be mostly climbing, while some will be mostly descending. Depending on how those ascents and descents are arranged, the average gradient while climbing could vary substantially. One of my courses that's just over 50 miles long has about 2600 feet of climbing, but most of those are packed into a couple of stretches. The longest of those is 9 miles long with an average 2.4% grade. Feet per mile is a useful metric for gauging the overall hilliness of a closed loop ride, but it needs to be used in conjunction with other metrics if you want a fine-grained comparison. A 50-mile out-and-back course that involves a steady climb of 2500 feet over 25 miles, then a steady descent on the return, is going to feel very different than one that has 15 miles on flat terrain, then a 2500-foot climb over 10 miles. They're both 50 feet per mile, though, over the entire course.