Guidesfrom the federal index

What Is My House Worth Since I Bought It? The Index Method, Step by Step

Take what you paid, multiply by how your area's FHFA index changed since then, and you have a checkable estimate. The formula, a worked example, and its limits.

The short answer

Multiply what you paid by how much your area’s house price index has risen since you bought. If you paid $310,000 and the index for your ZIP is 1.95 times what it was then, the estimate is $310,000 × 1.95 = $604,811. That is the whole method. It tells you what your home would be worth today if it had changed in value exactly the way the average home around it did. It does not look at your house at all, which is both its honesty and its limit.

The formula

Value today = purchase price × (index now ÷ index at purchase)

The index is the FHFA House Price Index, a public-domain federal series that measures average price changes in repeat sales or refinancings of the same properties. Because it follows the same homes over time, the ratio of two index values is a clean measure of how much prices in that area changed between those two dates, independent of what kind of homes happened to sell in either period. The index level itself means nothing on its own; only the ratio matters.

Which area

FHFA publishes the index at several levels, and the smallest one with data is the most specific answer. The order this site uses is ZIP code, then county, then metro area, then state (see what the index measures for why the smaller levels come with a warning label). A level is skipped when it has no index, when its index starts after your purchase date, when the value for your purchase period is missing, or when nothing newer than your purchase has been published. Whatever level is used, the answer should say so.

Which date

State and metro indexes are quarterly, so a March purchase is matched to the first quarter of that year. County and ZIP indexes are annual, so the same purchase is matched to the year. “Now” is the latest period FHFA has published, which trails the calendar: the quarterly file currently ends at 2026 Q2 and the annual ZIP and county files at 2025. An estimate is only as current as its series.

A worked example

You bought in March 2014 for $310,000 in ZIP 78704, in Austin, Texas.

FHFA’s annual index for ZIP 78704 was 1529.73 in 2014.
The latest published value is 2984.51, for 2025.
2984.51 ÷ 1529.73 = 1.95. Prices in the ZIP are +95.1% since your purchase year, about +6.3% a year compounded.
$310,000 × 1.95 = $604,811.

Run the same purchase through the Texas state index instead and you get 531.31 ÷ 241.28 = 2.20, so $310,000 × 2.20 = $682,635 (2014 Q1 to 2026 Q2). The two answers differ by $77,823. Neither is wrong. The ZIP figure describes one neighborhood through 2025; the state figure describes all of Texas through a later quarter. That spread is the reason the level and the periods have to be printed next to any number from this method.

The home value since purchase calculator does these four steps for any price, month, year and ZIP, prints the index values it used, and shows what every other level would have said for the same purchase.

What this method cannot know

Your house. It tracks the area’s average. A new kitchen, a leaking roof, a corner lot and a busy road are all invisible to it.
What you paid relative to the market. A bargain or an overpayment in 2014 is carried forward unchanged.
Sales the index never sees. The FHFA index is built from mortgages bought or guaranteed by Fannie Mae and Freddie Mac, so cash, jumbo, FHA and VA purchases are not in it (FHFA HPI FAQ).
Equity and proceeds. This is a value, not what you would clear after your mortgage balance, commissions and taxes.
The future. The index is history. Nothing in it says where prices go next.

It is an estimate of a typical outcome, not an appraisal. If you need a number that accounts for your specific house, that is what an appraiser is for.

Sources

FHFA House Price Index datasets, the master file and the annual county and ZIP files.
FHFA HPI frequently asked questions, on what the index includes.
FHFA HPI technical description, the repeat-sales method.

Try it: Home Value Since Purchase Calculator →

This guide is for informational purposes only. It is not an appraisal, and not financial, tax, lending or real-estate advice. Every estimate on this site tracks an area’s average, never a particular house. Confirm anything that matters with a licensed appraiser or your lender.

Last reviewed: September 2026 · Against the FHFA House Price Index (master file through 2026 Q2; annual ZIP file dated March 31, 2026).