According to the United States Census Bureau, the CDP has a total area of 4.0 square miles (10.3 km2), all land.[2] Mililani Mauka lies within the ʻEwa Moku on Oʻahu, more specifically the Waipiʻo Ahupuaʻa.[4][5] The ancestry was 4.5% German, 4.4% English, 4.0% Irish, 1.6% Portuguese, 1.5% Italian, 0.7% French, 0.7% Swedish, and 0.6% Danish.[4][5] The median household income was $119,981, with families having $136,755, married couples having $145,145, and non-families having $59,413.[4][5] Hawaii Department of Education operates public schools within the CDP.