ZIP Code 78664

78664 is one of Texas's ZIP codes, delivering to addresses in Round Rock, Williamson County.

City: Round Rock
County: Williamson County
State: Texas
Prefix: 786xx

Where this code sits

78664 is part of the 786xx range, the group of codes handled by one mail processing centre. Round Rock is served by 6 ZIP codes in total; the full list, with the county each falls in, is on the Round Rock page.

Round Rock Texas ZIP codes →

Area codes over the same ground

Postal and telephone geography are drawn separately, so these codes cover the area 78664 delivers to without sharing its boundary.

ZIP codes nearest 78664

The ZIP codes whose reference points sit closest to 78664.
ZIP code	Distance	Delivers to
ZIP code 78665	0.0 mi	Round Rock, TX
ZIP code 78681	0.8 mi	Round Rock, TX
ZIP code 78717	4.8 mi	Austin, TX
ZIP code 78764	4.8 mi	Austin, TX
ZIP code 78728	5.1 mi	Austin, TX
ZIP code 78660	5.5 mi	Pflugerville, TX
ZIP code 78691	5.9 mi	Pflugerville, TX
ZIP code 78634	6.0 mi	Hutto, TX

Straight-line distance between place reference points, not driving distance. Where a place has no Census Gazetteer point, its postal centroid is used instead.

Each point is the reference point for 78664, plotted from its record coordinates.

Reference points and footprint
Not an official NANPA boundary
Not a USPS delivery area

Scope ZIP code 78664. Source GeoNames US postal codes (2026-07 postal dump) and Census 2024 county Gazetteer (2024 Gazetteer). Updated 15 July 2026. A ZIP code is a set of delivery routes, not an area; the point shown is a record coordinate, not a centre.