Historical population
| Census | Pop. | Note | %± |
| 2010 | 4,451 | | — |
|---|
| 2020 | 4,698 | | 5.5% |
|---|
Mather first appeared as a census designated place in the 2010 U.S. census formed from part of deleted Rancho Cordova CDP and additional area.[18]
The 2020 United States census reported that Mather had a population of 4,698. The population density was 468.6 inhabitants per square mile (180.9/km2). The racial makeup of Mather was 52.3% White, 8.0% African American, 1.3% Native American, 15.3% Asian, 1.0% Pacific Islander, 6.7% from other races, and 15.4% from two or more races. Hispanic or Latino of any race were 19.9% of the population.[19]
The whole population lived in households. There were 1,528 households, out of which 43.5% included children under the age of 18, 59.2% were married-couple households, 8.0% were cohabiting couple households, 20.2% had a female householder with no partner present, and 12.6% had a male householder with no partner present. 15.7% of households were one person, and 4.6% were one person aged 65 or older. The average household size was 3.07.[19] There were 1,175 families (76.9% of all households).[20]
The age distribution was 26.7% under the age of 18, 8.9% aged 18 to 24, 28.5% aged 25 to 44, 26.2% aged 45 to 64, and 9.8% who were 65 years of age or older. The median age was 36.0 years. For every 100 females, there were 96.8 males.[19]
There were 1,558 housing units at an average density of 155.4 units per square mile (60.0 units/km2), of which 1,528 (98.1%) were occupied. Of these, 74.0% were owner-occupied, and 26.0% were occupied by renters.[19]
In 2023, the US Census Bureau estimated that the median household income was $140,941, and the per capita income was $48,729. About 2.6% of families and 3.6% of the population were below the poverty line.[21]