In terms of miles, the equivalent of a 20-kilometer race is approximately 12.43 miles, or 12 miles and 752.27 yards. One kilometer equals 0.621371 mile or a little more than half of a mile.
Other popular distances for runners are the 5- and 10-kilometer races. A 5-kilometer race is equal to approximately 3.1 miles, and a 10-kilometer race is 6.2 miles long. The 5-, 10- and 20-kilometer races all are shorter than a marathon, which is officially 26 miles and 385 yards or about 42.2 kilometers in length. Even a half-marathon is longer than a 20-kilometer race at 13.1 miles or 21 kilometers long.