Rocky Ridge, MD 21778 ZIP Code Profile

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Rocky Ridge, MD

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ZIP Code 21778: Basic Data & USPS Preferred City Name

Preferred Name, USPS
Rocky Ridge, MD 21778

  • ZIP Code Type: STANDARD
  • County: Frederick County
  • Centroid: Latitude 39.614, Longitude -77.341
  • Time Zone: Eastern Time Zone (UTC -5 hours)
  • Observes DST: Yes
  • Businesses Addresses: 10
  • PO Box Addresses: 11
  • Residential Addresses: 443
    • Multi-Family Addresses: 0
    • Single Family Addresses: 443

The ZIP Code maps and database are updated 4 times per year.
Database updated: February 1, 2018, Maps updated: February 1, 2018.

EXTREMELY LOCAL Demographic Data

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21778 ZIP Code Map

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Rocky Ridge, MD 21778 Data & Demographics (As of July 1, 2017)


Total Population 1,180
Daytime Population: Workers 134
Daytime Population: Residents 538
Total Daytime Population (TDP) 672
Ratio TDP/Total Population1 0.57
Population in Households 1,180
Population in Familes 1,006
Population in Group Qrtrs 0
Population Density2 66
Diversity Index3 12


Median Household Income $68,925
Average Household Income $82,984
Per Capita Income $30,873


Total Housing Units 469 (100%)
Owner Occupied HU 350 (74.6%)
Renter Occupied HU 89 (19.0%)
Vacant Housing Units 30 ( 6.4%)
Median Home Value $316,000
Average Home Value $382,357


Total Households 439
Average Household Size 2.69
Family Households 335
Average Family Size 3
  1. If the ratio of the TDP to Total Population is greater than 1, the location gains population during the day when commuting workers are present. If the ratio is less than 1, the location is more of a bedroom community where people commute to another place for work.
  2. Population Density = Total Population per square mile.
  3. The Diversity Index is a scale of 0 to 100 that represents the likelihood that two persons, chosen at random from the same area, belong to different race or ethnic groups. If an area's entire population belongs to one race AND one ethnic group, then the area has zero diversity. An area's diversity index increases to 100 when the population is evenly divided into two or more race/ethnic groups.


2010-2017 2017-2022
Population 0.61% 0.75%
Households 0.65% 0.76%
Families 0.5% 0.65%
Median Household Income   1.7%
Per Capita Income   2.39%

Rocky Ridge, MD 21778 - Peer Comparisons by Rank and Percentile

The table below compares 21778 to the other 456 ZIP Codes in Maryland by rank and percentile using July 1, 2017 data. The location Ranked # 1 has the highest value. A location that ranks higher than 75% of its peers would be in the 75th percentile of the peer group.

Variable Description Rank Percentile
Total Population # 343 25th
Population Density # 396 13th
Diversity Index # 420 8th
Median Household Income # 258 44th
Per Capita Income # 297 35th

Additional comparisons and rankings can be made with a VERY EASY TO USE Maryland Census Data Comparison Tool.

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