Walking at a moderate pace, it takes a person 45 to 60 minutes to walk 3 miles. This makes the average speed between 15 minutes and 20 minutes per mile.
The speed at which a person completes 1 mile or 3 miles depends on a few factors. The environment where the person is walking affects his speed. A walk on a flat surface is completed sooner than one on a rough terrain, such as a nature walk or a hiking environment. The person's health also changes his completion time. An overall healthier person can walk 3 miles at a faster pace than an unhealthy person.