How many people live in Mercer County, NJ?
Updated Apr. 6, 2026Refreshed annually
In 2024, there were about 392,100 people living in Mercer County, NJ. That makes Mercer County the 12th-most populous county in New Jersey. It is home to 4.1% of people living in the state.
392K
population of Mercer County, NJ (2024)
4.1%
County share of the New Jersey population (2024)
About 392,100 people lived in Mercer County, NJ in 2024.
Population estimates, 2000–2024
What are Mercer County, NJ’s age demographics?
About 65,100 Mercer County, NJ residents are aged 65 and older in 2024. That represents 16.6% of its population. For comparison, the age group represents 18% of New Jersey’s population and 18% in the US overall.
Another 86,300 Mercer County residents, or 22% of the population, were children under 18. For comparison, the age group represents 21.5% of New Jersey’s population and 21.6% in the US overall.
A lower share of Mercer County, NJ's population is aged 25–44 than the US as a whole.
Population estimates by age group, (2024)
What are Mercer County, NJ’s racial and ethnic demographics?
Hispanic residents make up 24.6% of the Mercer County, NJ population, higher than the national share of 20%. Mercer County, NJ also has a larger share of people identifying as non-Hispanic Black or African American (18.5%) than the US overall (12.6%).
In contrast, Mercer County’s non-Hispanic white population accounts for 41.4%, below the 57.5% nationwide, and the non-Hispanic American Indian and Alaska Native population makes up 0.15% of the county, compared with 0.72% nationally.
Racial and ethnic make up differ based on location. These figures reflect how people identified their race alone (not in combination with other races), and separate out Hispanic or Latino ethnicity, following Census reporting standards.
Mercer County, NJ has a higher share of a non-Hispanic Black or African American population than New Jersey as a whole.
Population estimates by race and ethnicity, (2024)
The largest city or town in Mercer County, NJ is Hamilton with about 93,900 residents in 2024.
Cities and towns in Mercer County, NJ ranked by population
Population (2024), includes only portions within county
| City or town | Population | |
|---|---|---|
| 1. | Hamilton | 93,911 |
| 2. | Trenton | 91,193 |
| 3. | Ewing | 35,858 |
| 4. | Lawrence | 32,388 |
| 5. | West Windsor | 32,241 |
| 6. | Princeton | 31,445 |
| 7. | East Windsor | 30,436 |
| 8. | Hopewell | 17,916 |
| 9. | Robbinsville | 15,928 |
| 10. | Hightstown borough | 5,978 |
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Methodology
USAFacts standardizes data, in areas such as time and demographics, to make it easier to understand and compare.
The analysis was generated with the help of AI and reviewed by USAFacts for accuracy.
Page sources
USAFacts endeavors to share the most up-to-date information available. We sourced the data on this page directly from government agencies; however, the intervals at which agencies publish updated data vary.
