Fairfax County vs Loudoun County
Two neighbouring counties and independent cities in Virginia, compared on population, size, income and housing. They share 18 mi of border.
Fairfax County
Virginia
Loudoun County
Virginia
Both outlines are drawn at true relative size. Loudoun County spans about 52.4 km at its widest.
Side by side
| Measure | Fairfax County | Difference | Loudoun County |
|---|---|---|---|
| Population | 1,167,873 | +159.7% | 449,749 |
| Change since 2020 | 1.7% | -4.7 pp | 6.4% |
| Land area | 391 sq mi | -24.2% | 515.7 sq mi |
| Population density | 2,987 per sq mi | +242.5% | 872 per sq mi |
| Median household income | $153,637 | -15.5% | $181,765 |
| Median home value | $732,800 | -1.5% | $743,800 |
| Median age | 39.1 | +2.4% | 38.2 |
| Households | 414,101 | +189.5% | 143,032 |
| Housing units | 430,047 | +192.5% | 147,003 |
Sources: US Census Bureau, Population Estimates Program, Vintage 2025 Population Estimates, released 26 March 2026; US Census Bureau, Gazetteer Files, 2025 Gazetteer Files, released 10 September 2025; US Census Bureau, American Community Survey, American Community Survey 2020-2024 5-Year Estimates, released 29 January 2026; US Census Bureau, County Adjacency File, 2025 County Adjacency File, released 15 September 2025. The difference column is computed here: the first county's figure against the second, expressed as a percentage of the second. The change-since-2020 row is the exception: two growth rates differ in percentage points (pp), not percent. Retrieved 30 August 2026.
What the numbers say
- Fairfax County holds about 2.6 times the population of Loudoun County: 1,167,873 against 449,749.
- Loudoun County covers more ground, at 515.7 square miles against 391.
- Fairfax County is the more crowded of the two, at 2,987 people per square mile against 872.
- Median household income is higher in Loudoun County, by 28,128 dollars a year.
- Since 2020, Fairfax County has grown by 1.7% and Loudoun County has grown by 6.4%.
- They share 18 mi of common border, which the Census Bureau publishes in its county adjacency file and which almost no other county reference presents.
Full pages
Want a different pair? Compare any two of the 3,144 US counties.
Rebuilt from source data 30 August 2026. How these figures are produced.