I have always wondered how they equate. I alternate days of running and riding fixed to work. It's 8 miles and riding usually takes 25 minutes with running taking 70-75 minutes. By that time differential, would it be 1 mile run equals 3 miles bike, assuming you do them both at the same effort level? I have no idea. I try to do both in the same cardio zone but I'm generally a faster cyclist than I am runner. Running takes significantly more out of me.