San Miguel is a census-designated place in Contra Costa County, California. San Miguel sits at an elevation of . The 2020 United States census reported San Miguel's population was 3,591.
According to the United States Census Bureau, the CDP has a total area of , all of it land.
The 2020 United States census reported that San Miguel had a population of 3,591. The population density was . The racial makeup of San Miguel was 79.0% White, 0.7% African American, 0.1% Native American, 8.6% Asian, 0.3% Pacific Islander, 2.0% from other races, and 9.3% from two or more races. Hispanic or Latino of any race were 8.0% of the population.
The census reported that 99.9% of the population lived in households and 0.1% lived in non-institutionalized group quarters.
There were 1,296 households, out of which 35.6% included children under the age of 18, 70.7% were married-couple households, 3.5% were cohabiting couple households, 15.3% had a female householder with no partner present, and 10.6% had a male householder with no partner present. 14.6% of households were one person, and 9.5% were one person aged 65 or older. The average household size was 2.77. There were 1,063 families (82.0% of all households).
The age distribution was 22.6% under the age of 18, 6.6% aged 18 to 24, 16.6% aged 25 to 44, 32.1% aged 45 to 64, and 22.1% who were 65years of age or older. The median age was 47.6years. For every 100 females, there were 94.3 males.
There were 1,318 housing units at an average density of , of which 1,296 (98.3%) were occupied. Of these, 90.7% were owner-occupied, and 9.3% were occupied by renters.
San Miguel is in the Walnut Creek Elementary School District and the Acalanes Union High School District.