San Mateo County, California Demographics
Population trends, housing costs, income, commuting, and health, all on one page.
San Mateo County, CA Population Density Map and Area Scores
Area Score
Health, income and education, each graded from F to A+. Explore interactive maps for deeper analysis.
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A+
Health Top gradeAmong the top 3 healthiest counties in California
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A
Income Above averageAmong the top 3 wealthiest counties in California
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A+
Education Top gradeAmong the top 5 best educated counties in California
Source: Map AI Methodology
Population: density and quick facts
| Metric | San Mateo County | California Avg | U.S. Average |
|---|---|---|---|
| Population | 733,246 | 39,245,658 | 337,468,954 |
| Population density (per sq mi) | 990.3 | 239.4 | 86.4 |
| Population growth (%/yr) | -0.48% | 0.19% | 0.59% |
| Median age | 41.4 | 35.5 | 37.3 |
| Households | 261,537 | 13,531,619 | 130,235,071 |
Population in San Mateo County declined by 0.2% from 2009 to 2024, reaching 733,246 in 2024.
Population Growth 2009–2024
Race & Ethnicity
Age & Sex
The largest generation in San Mateo County is Millennials, aged 29–44, at 23.9% of residents. That is 0.3 points above California as a whole.
- Gen Z 13–28 136,635 18.6% -3.1 pts
- Millennials 29–44 175,555 23.9% +0.3 pts
- Gen X 45–60 157,117 21.4% +1.6 pts
- Boomers 61–79 123,879 16.9% +1.6 pts
Residents by birth cohort, from the 2025 age distribution. The right-hand figure is how far each cohort's share sits above or below California, in percentage points. Children younger than Gen Z and the generations before the Boomers are counted in the population but not shown here, so these shares do not add up to 100%.
Male and female share
Women are 50.1% of the people living in San Mateo County and men 49.9%.
- Women 50.1% California 49.9%
- Men 49.9% California 50.1%
How many residents match a customer profile?
Residents matching this profile
100% of everyone living in San Mateo County
Pick an age range and a women/men split and the figure above answers with how many residents that profile reaches.
Economy
San Mateo County has a the economy index of A, which means it is very prosperous.
| Metric | San Mateo County | California Avg | U.S. Average |
|---|---|---|---|
| Median household income | $159,405 | $99,161 | $80,455 |
| Income growth (%/yr) | 6.20% | 5.57% | 4.80% |
| Unemployment rate | 4.8% | 6.6% | 5.2% |
The median household income in San Mateo County is about 61% higher than in California.
Housing
| Metric | San Mateo County | California Avg | U.S. Average |
|---|---|---|---|
| Median home price | $1,744,985 | $650,794 | $248,835 |
| Median rent | $2,920 | $2,036 | $1,407 |
| Homeownership rate | 58.2% | 55.9% | 65.2% |
The median home price in San Mateo County is about 49.8 years' worth of rent — buying at the median price costs roughly as much as paying the median rent of $2,920 per month for that long.
Commute Time & Mobility
Commuters in San Mateo County spend about 46 minutes on the road round trip each working day. Over a typical 250-day work year, that adds up to roughly 193 hours, about 8.0 full days, spent commuting.
| Metric | San Mateo County | California Avg | U.S. Average |
|---|---|---|---|
| One-way commute (min) | 23.2 | 23.5 | 22.4 |
| Round-trip commute (min) | 46.4 | 47.0 | 44.8 |
| Yearly time spent (hours) | 193 | 196 | 187 |
| Estimated yearly cost | $5,987 | $6,065 | $5,790 |
| Work from home | 24.3% | 17.2% | 15.0% |
| Highway traffic (vehicles/day) | 23,528 | 16,509 | 8,813 |
| Local road traffic (vehicles/day) | 3,407 | 2,449 | 1,355 |
Fastest commutes among counties in
California:
Inyo County (11.1 min), Mono County (12.0 min), Del Norte County (12.1 min).
Slowest:
Alpine County (31.3 min), San Benito County (31.2 min), Contra Costa County (31.0 min).
The average commute time in San Mateo County is about the same as in California.
Estimated yearly cost applies a single national wage rule of thumb (U.S. Bureau of Labor Statistics average hourly earnings), not a measurement of wages in this area. Traffic volume figures come from proprietary Ticon and TrafficZoom data.
Education & Households
San Mateo County has a education index of A+, which means it is exceptionally educated.
| Metric | San Mateo County | California Avg | U.S. Average |
|---|---|---|---|
| Bachelor's degree or higher | 50.3% | 33.0% | 31.6% |
| Average household size | 2.75 | 2.84 | 2.53 |
Highest education index among counties in
California:
Marin County (0.5), San Francisco County (0.4), Santa Clara County (0.4).
Lowest:
Colusa County (0.2), Merced County (0.2), Glenn County (0.2).
Health
San Mateo County has a health index of A+, which means it is exceptionally healthy.
| Metric | San Mateo County | California Avg | U.S. Average |
|---|---|---|---|
| Life expectancy (years) | 82.7 | 79.6 | 78.3 |
| Self-rated poor health | 10.8% | 16.4% | 16.3% |
| Smokers | 8.9% | 13.9% | 19.0% |
Highest health index among counties in
California:
San Francisco County (0.8), San Mateo County (0.8), Santa Clara County (0.8).
Lowest:
Lake County (0.8), Imperial County (0.8), Tulare County (0.8).
San Mateo County, CA Compared With Nearby Counties
San Mateo County, CA is the 5th largest of the 6 counties compared here, 733,246 residents against a local median of 1,163,035. The measure that sets San Mateo County, CA apart most is median home price: $1,744,985, 57% above the local median of $1,111,762.
Median household income tells the same story from another angle: $159,405 against a local median of $129,593, 23% above it. Every measure here with a clear better direction points the same way, so San Mateo County, CA is not trading one advantage for another, it reads stronger than its neighbours across the board. The counties themselves spread $715,504 on median home price, so San Mateo County, CA sits at one end of an already wide local range rather than apart from it. San Mateo County, CA has the highest median home price of the 6 areas compared here.
| Area | Population | Median household income | Median home price | Commute |
|---|---|---|---|---|
| San Mateo County, CA | 733,246 | $159,405 #2/6 | $1,744,985 #1/6 | 23.2 min #3/6 |
| San Francisco County, CA | 829,818 | $140,554 | $1,276,188 | 28.7 min |
| Alameda County, CA | 1,648,382 | $129,593 | $833,751 | 28.3 min |
| Santa Cruz County, CA | 264,809 | $111,078 | $1,111,762 | 21.0 min |
| Contra Costa County, CA | 1,163,035 | $127,405 | $663,272 | 31.0 min |
| Santa Clara County, CA | 1,901,257 | $165,940 | $1,378,776 | 22.9 min |
Frequently Asked Questions
Common questions about San Mateo County, California.
How many people live in San Mateo County, California?
About 733,246 people live in San Mateo County, California, in 261,537 households of 2.8 people on average. The median age is 41.4, so residents are older than the U.S. median of 37.3 by about 4 years.
Is San Mateo County, California mostly urban or rural?
Averaged over its land area, San Mateo County, California has 990 people per square mile, a density typical of a mix of suburbs, small towns and farmland. That is about 11 times the U.S. average of 86.
How affordable is housing in San Mateo County, California?
The median home costs 10.9 times the median household income ($1,744,985 against $159,405), compared with 3.1 times nationally. A ratio of about 3 is traditionally considered affordable. Median rent of $2,920 a month takes about 22% of the median household's income, below the 30% level at which HUD considers renters cost-burdened.
What share of adults in San Mateo County, California have a college degree?
50.3% of adults in San Mateo County, California hold a bachelor's degree or higher (about 5 in 10), well above the U.S. share of 31.6%.
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