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Zip Code 78665 — Round Rock, TX

78665 is a ZIP Code associated with Round Rock, TX, located within Williamson. The postal region supports an estimated population of 66,171 residents across Data Pending housing units, with a population density of 1,061.1 people per square mile.
WorldPlaceData database updated: October 2026

📍 View location on OpenStreetMap (30.550380, -97.636810)

Data MetricLocal Statistic
Postal / Zip Code78665
Primary CityRound Rock
State / ProvinceTX
CountyWilliamson
Total Population66,171
Median Household IncomeData Pending
Total Housing UnitsData Pending
Population Density1,061.1 people/sq mi
TimezoneAmerica/Chicago

How 78665 Compares

MetricZIP 78665Williamson CountyTX State Average
Population66,171591,18730,188,035
Median IncomeData PendingN/AN/A
Population Density1,061.1 /sq mi----

Nearby ZIP Codes

ZIP CodeCityDistancePopulationMedian Income
Zip 78664Round Rock3.2 mi62,060N/A
Zip 78681Round Rock5.0 mi56,691N/A
Zip 78634Hutto5.6 mi46,413N/A
Zip 78728Austin7.3 mi26,777N/A
Zip 78660Pflugerville7.8 mi124,834N/A

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 →