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US ZIP Code Profile

ZIP Code 78665
Round Rock, Texas

ZIP code 78665 is in Round Rock, located in Williamson County, Texas, within the Austin-Round Rock metro area. Its 2020 Census population was 61,577. The estimated median adjusted gross income per tax return is $69,970, and about 13% of filers report $200,000 or more.

2020 Population
61,577
Census ZCTA
County
Williamson
FIPS 48491
Median income (est.)
$69,970
IRS SOI 2022
Land Area
18.759 mi²
+ 0.294 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
Coordinates30.543255, -97.6452
Land / Water Area18.759 mi² land · 0.294 mi² water

02Income & Economics

Distribution of the 30,230 individual tax returns filed in 78665 by adjusted gross income bracket (IRS SOI, 2022).

< $25K
19.6%
$25K–$50K
19.3%
$50K–$75K
13.9%
$75K–$100K
10.0%
$100K–$200K
24.2%
$200K+
13.0%
The $200,000+ bracket accounts for 43% of 78665's total adjusted gross income, from 13% of returns — a concentration that drives the gap between the median ($69,970) 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 78665's IRS income metrics, 2020–2022.

Median income (2021→2022)
$69,970
▲ 5.5%
Filers earning $200K+
13.0%
▲ 2.0 pt
Total filers
30,230
▲ 4.0%
GET /zipc/v2/zipcodes/78665/soi?year=… $61K 2020 $66K 2021 $70K 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 78665 ZCTA.

2010
35,985
 
2020
61,577
▲ +71.1%

05Nearby ZIP Codes — Live Radius Search

Drag the slider to filter ZIP codes by distance from 78665. Powered by the same radius endpoint developers call from the API.

GET /zipc/v2/radius

ZIP codes within range of 78665

Round Rock and its immediate neighbors, sorted by distance.

3 mi
GET /zipc/v2/distance

Distance from 78665 to any ZIP

Enter a 5-digit ZIP to calculate the distance.

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 AliasesRound Rock

07Frequently Asked Questions

What county is ZIP code 78665 in?

ZIP code 78665 is in Williamson County, Texas (county FIPS code 48491).

What city is ZIP code 78665?

The primary USPS city for 78665 is Round Rock, TX.

What metro area (MSA) is 78665 in?

78665 is part of the Austin-Round Rock, TX Metro Area (MSA code 12420).

What is the population of ZIP code 78665?

The 2020 Census population of 78665 was 61,577 residents.

What is the median income in ZIP code 78665?

Based on IRS Statistics of Income data, the estimated median adjusted gross income per tax return in 78665 is about $69,970, with around 13% of filers reporting $200,000 or more. Note that adjusted gross income is a tax measure and differs from U.S. Census household income.