Zip Code 20878 — Gaithersburg, MD
20878 is a ZIP Code associated with Gaithersburg, MD, located within Montgomery. 20878 ranks #2 out of 48 ZIP codes in Montgomery County by population (and #3 out of 477 in MD). The area supports an estimated population of 66,115 residents across Data Pending housing units, with a population density of 1,248.3 people per square mile.
WorldPlaceData database updated: October 2026
📍 View location on OpenStreetMap (39.113760, -77.247810)
| Data Metric | Local Statistic |
|---|
| Postal / Zip Code | 20878 |
| Primary City | Gaithersburg |
| State / Province | MD |
| County | Montgomery |
| Total Population | 66,115 |
| Median Household Income | Data Pending |
| Total Housing Units | Data Pending |
| Population Density | 1,248.3 people/sq mi |
| Timezone | America/New_York |
How 20878 Compares
| Metric | ZIP 20878 | Montgomery County | MD State Average |
|---|
| Population | 66,115 | 1,076,754 (Total) | 6,205,597 (Total) |
| Average ZIP Income | Data Pending | N/A | N/A |
| Population Density | 1,248.3 /sq mi | -- | -- |
| County Pop Rank | #2 of 48 | -- | -- |
Nearby ZIP Codes
Data Sources & Methodology: Geographic coordinates and ZIP Code assignments are derived from underlying geographic and postal datasets. Note that ZIP Codes are USPS postal delivery areas, while Census ZCTAs are statistical approximation areas. Read full methodology →