The 2014 Nampa, Idaho, population is 81,667. There are 2,618 people per square mile (population density). The median age is 29.8. The US median is 37.2. 55.81% of people in Nampa, Idaho, are married. 12.40% are divorced. The average household size is 2.95 people. 41.01% of people are married, with children. 18.44% have children, but are single. 90.22% of people are white, 0.40% are black, 0.87% are asian, 0.90% are native american, and 3.75% claim 'Other'.