 The average household size was 2.61, and the average family size was 3.15.Data indicates that 28.7% of Plano's population was under the age of 18, 7.0% was 18 to 24, 36.5% was 25 to 44, 22.9% was 45 to 64, and 4.9% was 65 years of age or older.The median age was 34 years.