States › Texas › Williamson County › ZIP 78642
ZIP code
ZIP 78642
Williamson County · Austin-Round Rock-San Marcos, TX · Texas
FHFA notes: The FHFA HPI is a broad measure of the movement of single-family house prices. The FHFA HPI is a weighted, repeat-sales index, meaning that it measures average price changes in repeat sales or refinancings on the same properties. FHFA describes its ZIP code indexes as developmental: they may be revised as new data arrive or methods change, and the index does not give a dollar value for any home.
Williamson County, Texas ZIP 78642 has 30 years of index history. Since 1996 the FHFA index has moved from 100 to 443, a change of +342.9%.
Over the ten years to 2025 the index rose +107.7%, about +7.6% a year: above Williamson County (+99.8%), well above Texas (+88.2%) and well above the national index (+85.0%). The change over 2024–2025 was +0.8%.
By decade, the strongest was the 2010s (+62.3%) and the weakest the 2000s (+36.1%).
The index did not fall 5% or more from a peak between 2006 and 2012, which is unusual; small samples in a ZIP code can also mask movements.
Building activity is measured at county level: Williamson County authorised 4,277 housing units in the 12 months to August 2026, 5.7 per 1,000 residents, 90% of them single-family.
Same span, five levels
| Change in the FHFA index | ZIP 78642 | Williamson County | Austin-Round Rock-San Marcos area | Texas | United States |
|---|---|---|---|---|---|
| 1 year (2024–2025) | +0.8% | −1.0% | −1.4% | +0.8% | +2.8% |
| 5 years (2020–2025) | +55.2% | +43.3% | +35.5% | +43.5% | +47.0% |
| 10 years (2015–2025) | +107.7% | +99.8% | +87.5% | +88.2% | +85.0% |
| 20 years (2005–2025) | +193.9% | +190.3% | +193.3% | +147.8% | +79.1% |
| Since 2000 | +242.9% | +216.0% | +237.1% | +195.2% | +158.3% |
| Since 1996 | +342.9% | +280.0% | +332.1% | +252.5% | +214.5% |
| 10-year annualised | +7.6% | +7.2% | +6.5% | +6.5% | +6.3% |
| 20-year annualised | +5.5% | +5.5% | +5.5% | +4.6% | +3.0% |
Every column uses FHFA's annual all-transactions index family and the same start and end years, so the figures are directly comparable. A dash means the level has no index for that span.
Decade by decade
| Decade | Change | United States | |
|---|---|---|---|
| 2000s (2000–2010) | +36.1% | +29.7% | |
| 2010s (2010–2020) | +62.3% | +35.5% | |
| 2020s so far (2020–2025) | +55.2% | +47.0% |
FHFA reports each index with a value of 100 in its base period, the first year the area has enough transactions (1996 here). A decade's change is the index at the end of the decade divided by the index at the start, so it does not depend on the base year; the United States column covers the same years. Decades before 1996 are not shown.
Peak-to-low declines
Falls of 5% or more from a previous high in the annual index, and the year the earlier peak was regained.
No decline of 5% or more from a peak appears in the annual index for this area.
Building permits in Williamson County
Permits are reported by county and by permit-issuing place, not by ZIP code. Housing units authorised in Williamson County, latest 12 months.
Housing units authorised in Williamson County by month, Sep 2025 to Aug 2026single-family2+ unit buildings
Full permit history and every city in Williamson County
Other ZIP codes in Williamson County
Ranked by ten-year change in the FHFA index; ZIP 78642 ranks 3 of 13 with an index through 2025.
| ZIP | 1 year | 10 years | Since 2000 | Index through |
|---|---|---|---|---|
| 78615 | +60.0% | +251.0% | — | 2022 |
| 78717 | +41.1% | +177.2% | +213.8% | 2022 |
| 78634 | +1.1% | +117.8% | +234.4% | 2025 |
| 76574 | −0.5% | +114.5% | +218.8% | 2025 |
| 78626 | −0.8% | +106.4% | +237.8% | 2025 |
| 78664 | −0.1% | +106.4% | +204.6% | 2025 |
| 78681 | −0.9% | +103.7% | +226.0% | 2025 |
| 78613 | −3.7% | +94.9% | +208.4% | 2025 |
| 78628 | −2.5% | +94.6% | +202.2% | 2025 |
| 78665 | +3.5% | +93.0% | +175.9% | 2025 |
| 78633 | −0.9% | +90.8% | +174.4% | 2025 |
| 78729 | 0.0% | +86.4% | +214.0% | 2025 |
All 16 ZIP codes in Williamson County
Questions and answers
How much have home values in ZIP 78642 risen over 10 years?
The FHFA house price index for 78642 rose +107.7% between 2015 and 2025, about +7.6% a year compounded. Over five years the change was +55.2% and over one year +0.8%.
How does 78642 compare with Williamson County?
Over the same ten years to 2025, Williamson County rose +99.8%, Texas +88.2% and the United States +85.0%, against +107.7% for the ZIP. Among 13 ZIP codes in the county with an index through 2025, 78642 ranks 3 by ten-year change.
What happened to prices in 78642 after 2007?
The index for 78642 shows no decline of 5% or more from a 2005–2008 peak. Nationally the index fell −21.3% from 2007 to 2012.
How many homes are being built in 78642?
Building permits are published by place and county, not by ZIP. Williamson County authorised 4,277 housing units in the 12 months to August 2026, −34.3% on the previous 12 months. The county page lists permits by month and by city.
Where does the index for this ZIP come from?
From the Federal Housing Finance Agency's annual five-digit ZIP code house price index (all-transactions), last updated March 31, 2026. FHFA labels the ZIP-level indexes developmental: they are calibrated on appraisal values and sales prices for mortgages bought or guaranteed by Fannie Mae and Freddie Mac, and may be revised. The index tracks price changes for the same homes over time; it does not give a dollar value for any home.
Provenance
Index: Federal Housing Finance Agency, annual house price index for five-digit ZIP codes (all-transactions, developmental), last updated March 31, 2026, values 1996–2025, public domain. County, state and national comparison series are FHFA's annual indexes for those levels from the same release. ZIP to county assignment uses the Census Bureau's 2020 ZCTA-to-county relationship file (largest land share); county to metro uses OMB's July 2023 delineations. Permits: Census Bureau Building Permits Survey through August 2026. Errors in processing are corrected at the next build; see corrections. FHFA HPI datasets.