Clay is a census-designated place in Sacramento County, California. Clay sits at an elevation of . The 2020 United States census reported Clay's population was 1,252.
According to the United States Census Bureau, the CDP covers an area of 6.8 square miles (17.5 km<sup>2</sup>), all of it land.
Clay first appeared as a census designated place in the 2010 U.S. census.
The 2020 United States census reported that Clay had a population of 1,252. The population density was . The racial makeup of Clay was 874 (69.8%) White, 19 (1.5%) African American, 23 (1.8%) Native American, 47 (3.8%) Asian, 1 (0.1%) Pacific Islander, 130 (10.4%) from other races, and 158 (12.6%) from two or more races. Hispanic or Latino of any race were 284 persons (22.7%).
The whole population lived in households. There were 421 households, out of which 107 (25.4%) had children under the age of 18 living in them, 282 (67.0%) were married-couple households, 17 (4.0%) were cohabiting couple households, 74 (17.6%) had a female householder with no partner present, and 48 (11.4%) had a male householder with no partner present. 62 households (14.7%) were one person, and 44 (10.5%) were one person aged 65 or older. The average household size was 2.97. There were 333 families (79.1% of all households).
The age distribution was 245 people (19.6%) under the age of 18, 100 people (8.0%) aged 18 to 24, 252 people (20.1%) aged 25 to 44, 388 people (31.0%) aged 45 to 64, and 267 people (21.3%) who were 65years of age or older. The median age was 46.4years. For every 100 females, there were 100.0 males.
There were 447 housing units at an average density of , of which 421 (94.2%) were occupied. Of these, 388 (92.2%) were owner-occupied, and 33 (7.8%) were occupied by renters.