Method

The files these numbers come from

All 4 are published by the US Census Bureau, are works of the United States government, and are in the public domain. Each entry names what it supplies, the file itself, the day this site downloaded it, and the address it came from, so that any figure here can be recomputed from the same bytes.

1. Geographic Relationship File, 2026 vintage. Gives which unified, elementary and secondary school district each census block belongs to, and which ZIP Code Tabulation Area it falls in. Files: public_grfc_cur26_XX.txt, one per state. Retrieved 2026-09-03 from www2.census.gov/geo/docs/maps-data/data/grf/2026/.

2. 2020 Census Redistricting Data, PL 94-171. Gives housing units (H1_001) and residents (P1_001) in each census block. Files: 01-Redistricting_File--PL_94-171/<state>/xx2020.pl.zip, one per state. Retrieved 2026-09-03 from www2.census.gov/programs-surveys/decennial/2020/data/.

3. Census Gazetteer 2025. Gives district names, grade ranges and land areas, and the land area of each ZIP Code Tabulation Area. Files: 2025_Gaz_unsd, _elsd, _scsd and _zcta_national.zip. Retrieved 2026-09-03 from www2.census.gov/geo/docs/maps-data/data/gazetteer/2025_Gazetteer/.

4. 2020 ZIP Code Tabulation Area relationship files. Gives which places, county subdivisions and counties each ZIP Code Tabulation Area overlaps, and by how much land. Files: tab20_zcta520_place20, _cousub20 and _county20_natl.txt. Retrieved 2026-09-06 from www2.census.gov/geo/docs/maps-data/data/rel2020/zcta520/.

What is exact here, and what is not

Exact, 2 of them: which school district each census block belongs to, in each of the two grade bands; and how many housing units and how many residents each block holds. Those come from the files unchanged, and so does every share, count and ranking that is nothing more than a sum of them.

Not exact, 4 of them, and each is named where its number appears rather than only here: the ZIP Code area itself, which approximates a set of mail delivery routes with a set of census blocks; the age of the housing count, taken in 2020 and laid against 2026 boundaries, which understates the newest subdivisions and overstates cleared ground; the crossing between the two grade bands on a district page, which spreads a district's homes across the other band in proportion rather than following an address, because the file names the two districts of a block and not the path a household takes between them; and the place name printed beside a ZIP Code, which is the place covering the most land inside the area rather than the city the Postal Service prints on an envelope, because no federal file publishes the second.

Where these numbers come from

School district boundaries come from the Census Bureau's Census Geographic Relationship File, current 2026 vintage, which assigns every census block to a unified district or to an elementary and a secondary district. Homes and residents in each block come from the 2020 Census Redistricting Data (PL 94-171), H1_001 and P1_001. The ZIP Code areas come from the same Geographic Relationship File, block to ZIP Code Tabulation Area. District names and grade ranges come from the Census Gazetteer 2025, with 2020 for districts no longer listed.

The place name printed beside a ZIP Code comes from the Census 2020 ZIP Code Tabulation Area relationship files: place, county subdivision and county, taken 2026-09-06. It is a label rather than a measurement: the Census Bureau does not publish which post office a ZIP Code belongs to, so the place named is the one covering the most land inside the area, not the city the Postal Service prints on an envelope.

Everything else on this page — the shares, the counts of districts per ZIP, the comparison between the two grade bands, the rankings — is computed here from those files. The source publishes none of it. Snapshot taken 2026-09-03.

How a share is worked out

The Census Bureau assigns every one of the country's census blocks to a school district, and separately records how many housing units and residents each block holds. It also publishes which ZIP Code Tabulation Area each block falls in. Grouping the blocks of one ZIP Code area by district gives the share of that area's homes each district holds. That grouping is the whole of what this site does.

Homes rather than land area, deliberately. A district that receives an empty field covers a large share of a ZIP Code's surface and none of its people; measuring by area would make it look like an answer.

Two bands, because there are two answers

A block belongs either to one unified district, which runs all grades, or to an elementary district and a secondary district together. So the homes of a ZIP Code area divide twice: once for elementary grades and once for high school. Neither division ever counts a home twice: each sum is checked against the area’s own housing count, and where a district carries no grade range in the file at all it is left out of the band that would otherwise overflow. The two sums need not name the same districts. In 2,682 ZIP Code areas they do not.

Where the two sums do not agree, the difference is homes with no district of that kind. Across the country 47,429 homes have no school district at all: military installations, tribal land and unorganized territory.

What is deliberately not here

No school ratings, no test scores, no rankings of district quality. Those numbers correlate strongly with the income and composition of the households already living in a district, and publishing them next to a boundary turns a reference into a sorting tool. This site answers where the lines are, and stops.

No individual addresses. The lookup computes an answer for any of the 33,555 ZIP Code areas in the country, and 172 of them have a page of their own; the rest are answered by the lookup alone. A ZIP Code earns a page when its set of districts is unique in the country and its two grade bands have something to disagree about, and a district earns one when it is large or unusual enough to have something of its own to say.

Corrections

If a figure here does not match the Census Bureau files, tell us which page and which row: hello@districtbyzip.com. The parsing is mechanical, so a mismatch is a bug in our code and we want it.

What to do next

Ask the district office to confirm your street address. A district settles that question on its own site: look for a school locator, a find my school tool, or an attendance zone map. Where there is none, ask the office itself.

A ZIP Code is a set of mail delivery routes, not a boundary: 17,865 of the 33,555 ZIP Code areas in the country with homes in them are served by more than one school district, and the line between two of them runs along streets. Only the district can say which side of that line an address is on.

This site links to no district website. None of the federal files it is built from publishes one, and a guessed address is worse than none. It is the district office, not a search engine, that settles an address.

If a house purchase depends on the answer, ask the district itself for written confirmation of that exact address. A listing is not a district record, and neither is this page.