Depending on weight and pace, a person burns about 640 to 1,008 calories in an 8-mile walk. According to Prevention, a 140-pound person burns about 200 calories for every 30 minutes of walking at a 4.5 mph pace.
Most people begin walking a mile at a 20-minute pace and may develop an athletic 12-minute mile pace over time to burn more calories. The faster a person walks, the faster his heart uses oxygen, a key component in the calorie-burning process of the body. A quicker pace also means that a person walks more mileage in less time. According to SparkPeople, the accurate estimate of burned calories depends on a person's weight and time spent walking at a specific pace. Using an online calorie calculator is a great way to determine the calories burned for specific weight ranges.
An 8-mile walk takes an average two hours to complete if a person walks at a pace of 4 mph. For a person weighing 200 pounds, this translates to a 15-minute mile pace and a huge difference in calories burned from a 20-minute mile pace. At a 15-minute mile pace, a person weighing 200 pounds burns 864 calories in two hours and completes an 8-mile walking workout. At a consistent 20-minute mile pace, this same person only burns 624 in two hours and still needs another 40 minutes of walking to complete an 8-mile walking workout.