5k race = 3.1 miles. Most beginner runners will take an average time to finish a 5k race of 30 - 40 minutes. 10k race = 6.2 miles. The typical time it takes to do a 10k race is 1 - 1 1/2 hours. Half marathon = 13.1 miles, 21.7 kilometres. A respectable time it takes to do a half marathon is 2 - 2 1/2 hours. Marathon = 26.2 miles, 41.2 kilometres. The average time it takes runners to do a marathon is between 4 - 5 hours.