How many biking miles equal 1 walking mile?

Hi,

 It's very diffcult to compare the two since there are completely different exercises. They involve different usages of your muscles, and there is the fact you have to compare it by uphill, downhill, or flat ground which makes it a little bit more tricky. A way to comapre the two would be to look at the avg number of calories you burn doing each, and figure out the ratio of the amount of calories burned in the same time spa.