Cluster sampling refers to a type of sampling method . With cluster sampling, the researcher divides the population into separate groups, called clusters. Then, a simple random sample of clusters is selected from the population. The researcher conducts his analysis on data from the sampled clusters.
If you are running around an actual football field (100 yds x 50 yds) a mile would be 5.9 laps (1 mi = 1760 yds/300 = 5.86667). A standard racetrack around a football field should be 440 yds, so 4 laps should be a mile there (1760/440 = 4).
If however you are asking about a running track the answer is 4 laps for a standard 400m (440 yard) and 8 laps (220 yards) for a standard indoor track. It depends on the length of the lap. Modern running laps are 400 meters, and in that case one mile is: