ZIP Codes in San Marcos, TX
San Marcos uses 1 ZIP code, all in Hays County. Pick one below for details, or look up the full nine-digit ZIP+4 for a specific street address.
All 1 San Marcos ZIP codes
| ZIP | Type | County | Population |
|---|---|---|---|
| 78666 | standard | Hays | 88,583 |
Finding a ZIP+4 in San Marcos
Knowing which of these 1 ZIP codes covers an address only gets you partway. The four-digit extension identifies the specific delivery point — typically one side of one block. Two houses facing each other on the same San Marcos street almost always have different ZIP+4 codes even though they share all five leading digits.
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Upload a CSV of San Marcos addresses and download it complete.