Median Age in San Mateo County, CA
ACS 2024 5-Year Estimates
40.9 years
Rank #1,820/3,222 · #21 in CA
44th
San Mateo 40.9 years
CA 37.9 years +7.9%
US 38.9 years +5.1%
Median Age Trend
Rankings →Percentile Rank Over Time
Year-over-Year Age Change
National Distribution
How San Mateo County's median age of 40.9 years compares to all 3,222 U.S. counties. Values range from 21.4 years to 86.2 years.
Distribution of Median Age Across All Counties
Ranking Context
Counties ranked closest to San Mateo County for median age.
Nearby Rankings
Full ranking →| #1,817 | Jefferson County, WV | 41.0 years |
| #1,818 | Cross County, AR | 40.9 years |
| #1,819 | Phillips County, AR | 40.9 years |
| #1,820 | San Mateo County, CA | 40.9 years |
| #1,821 | Lincoln County, CO | 40.9 years |
| #1,822 | Phillips County, CO | 40.9 years |
| #1,823 | Jefferson County, GA | 40.9 years |
About Median Age
San Mateo County, California has a median age of 40.9 years, ranking #1,820 of 3,222 counties nationwide — 5.1% above the national value of 38.9 years. Within California, it ranks #21 of 58. This places it in the 44th percentile nationally.
The median age of the total population. Source: U.S. Census Bureau, American Community Survey 2024 5-Year Estimates. All values are estimates derived from survey samples and are subject to margin of error. For more information, see our methodology.