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US ZIP Code Profile

ZIP Code 78681
Round Rock, Texas

ZIP code 78681 is in Round Rock, located in Williamson County, Texas, within the Austin-Round Rock metro area. Its 2020 Census population was 57,503. The estimated median adjusted gross income per tax return is $79,185, and about 19% of filers report $200,000 or more.

2020 Population
57,503
Census ZCTA
County
Williamson
FIPS 48491
Median income (est.)
$79,185
IRS SOI 2022
Land Area
21.786 mi²
+ 0.152 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
Coordinates30.534424, -97.72574
Land / Water Area21.786 mi² land · 0.152 mi² water

02Income & Economics

Distribution of the 25,410 individual tax returns filed in 78681 by adjusted gross income bracket (IRS SOI, 2022).

< $25K
20.5%
$25K–$50K
16.1%
$50K–$75K
12.0%
$75K–$100K
8.8%
$100K–$200K
23.6%
$200K+
19.1%
The $200,000+ bracket accounts for 56% of 78681's total adjusted gross income, from 19% of returns — a concentration that drives the gap between the median ($79,185) 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 78681's IRS income metrics, 2020–2022.

Median income (2021→2022)
$79,185
▲ 5.7%
Filers earning $200K+
19.1%
▲ 1.6 pt
Total filers
25,410
▲ 1.2%
GET /zipc/v2/zipcodes/78681/soi?year=… $70K 2020 $75K 2021 $79K 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 78681 ZCTA.

2000
31,958
 
2010
50,606
▲ +58.4%
2020
57,503
▲ +13.6%

05USPS 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 AliasesAustin, Round Rock

06Frequently Asked Questions

What county is ZIP code 78681 in?

ZIP code 78681 is in Williamson County, Texas (county FIPS code 48491).

What city is ZIP code 78681?

The primary USPS city for 78681 is Round Rock, TX.

What metro area (MSA) is 78681 in?

78681 is part of the Austin-Round Rock, TX Metro Area (MSA code 12420).

What is the population of ZIP code 78681?

The 2020 Census population of 78681 was 57,503 residents.

What is the median income in ZIP code 78681?

Based on IRS Statistics of Income data, the estimated median adjusted gross income per tax return in 78681 is about $79,185, with around 19% of filers reporting $200,000 or more. Note that adjusted gross income is a tax measure and differs from U.S. Census household income.