You also have to take into account running/cycling economy. Someone who has terrible form and swings their arms too much/rocks back and forth is going to burn way more calories per mile running than a smooth, efficient runner.

A good "average" that most runners use is about 100 calories per mile. This is regardless of speed, because a person running 9 miles per hour will run a mile in less time than someone running 6 miles per hour, but calories per mile will average out to be pretty close.

There are a ton of variables at play here, but I have also heard that you can do about 3 to 1 (as previously stated) biking to running. But I would think this is for distance, not time.