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US ZIP Code Profile

ZIP Code 78664
Round Rock, Texas

ZIP code 78664 is in Round Rock, located in Williamson County, Texas, within the Austin-Round Rock metro area. Its 2020 Census population was 60,287. The estimated median adjusted gross income per tax return is $50,796, and about 7% of filers report $200,000 or more.

2020 Population
60,287
Census ZCTA
County
Williamson
FIPS 48491
Median income (est.)
$50,796
IRS SOI 2022
Land Area
16.577 mi²
+ 0.092 mi² water

01Location & Geography

Authoritative geographic identifiers from the U.S. Census Bureau, ANSI, and FIPS standards.

Primary CityRound Rock, TX
CountyWilliamson County (FIPS 48491)
StateTexas (FIPS 48)
Metro Area (MSA)Austin-Round Rock, TX Metro Area (12420)
Census Region / DivisionSouth Region · West South Central Division
Coordinates30.505413, -97.647285
Land / Water Area16.577 mi² land · 0.092 mi² water

02Income & Economics

Distribution of the 27,970 individual tax returns filed in 78664 by adjusted gross income bracket (IRS SOI, 2022).

< $25K
23.6%
$25K–$50K
25.9%
$50K–$75K
17.4%
$75K–$100K
9.9%
$100K–$200K
16.3%
$200K+
6.9%
The $200,000+ bracket accounts for 31% of 78664's total adjusted gross income, from 7% of returns — a concentration that drives the gap between the median ($50,796) and the average.
Estimated median = median adjusted gross income per tax return, interpolated from IRS SOI brackets. Differs from U.S. Census household income.

03Income Over Time

Year-over-year change in 78664's IRS income metrics, 2020–2022.

Median income (2021→2022)
$50,796
▲ 7.7%
Filers earning $200K+
6.9%
▲ 1.1 pt
Total filers
27,970
▲ 1.0%
GET /zipc/v2/zipcodes/78664/soi?year=… $44K 2020 $47K 2021 $51K 2022
Median = adjusted gross income per return, interpolated from IRS SOI brackets. Figures are nominal (not inflation-adjusted).

04Population Trend

Decennial U.S. Census population for the 78664 ZCTA.

2000
46,097
 
2010
52,932
▲ +14.8%
2020
60,287
▲ +13.9%

05Nearby ZIP Codes — Live Radius Search

Drag the slider to filter ZIP codes by distance from 78664. Powered by the same radius endpoint developers call from the API.

GET /zipc/v2/radius

ZIP codes within range of 78664

Round Rock and its immediate neighbors, sorted by distance.

3 mi
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Distance from 78664 to any ZIP

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06USPS Postal Details

Delivery and facility attributes from the monthly USPS dataset.

ZIP ClassificationNon-Unique Zip
Facility TypePost Office
Carrier Route SortD
USPS Finance Number487805
City AliasesOld Round Rock, Round Rock, Three Point

07Frequently Asked Questions

What county is ZIP code 78664 in?

ZIP code 78664 is in Williamson County, Texas (county FIPS code 48491).

What city is ZIP code 78664?

The primary USPS city for 78664 is Round Rock, TX.

What metro area (MSA) is 78664 in?

78664 is part of the Austin-Round Rock, TX Metro Area (MSA code 12420).

What is the population of ZIP code 78664?

The 2020 Census population of 78664 was 60,287 residents.

What is the median income in ZIP code 78664?

Based on IRS Statistics of Income data, the estimated median adjusted gross income per tax return in 78664 is about $50,796, with around 7% of filers reporting $200,000 or more. Note that adjusted gross income is a tax measure and differs from U.S. Census household income.