ZIP codes and county lines in Hawaii

None of the 97 ZIP code areas in Hawaii overlap more than one county. Every one sits inside a single county, which is unusual: nationally 30.1% are split.

ZIP code areas: 97
In more than one county: 0
At least 5% in a second county: 0
Cross a state line: 0

How Hawaii compares

Hawaii ranks 51 of 52 (the 50 states, DC and Puerto Rico) by the share of its ZIP code areas that overlap more than one county.

Every split ZIP code area in Hawaii

There are none to list. A ZIP-based list in Hawaii still has the other problems the ZIP list audit looks for: the same ZIP in two territories, Excel dropping leading zeros, and PO box ZIPs with no area at all.

What to do with this

If a ZIP code in your list is split, the ZIP alone cannot tell you which county an address is in. For most work that is fine. It matters when the county decides something: a sales tax rate, a licence, a franchise agreement written by county, or a service area somebody promised by county name.

The ZIP list audit checks your own list against the same Census data in your browser, and the ZIP spreadsheet comparison covers when a ZIP list is enough and when it is not.

What these numbers are, and are not

A ZCTA is not quite a ZIP code. ZIP Code Tabulation Areas are the Census Bureau's approximations of ZIP code areas, built by grouping census blocks by the ZIP codes of the addresses in them. USPS ZIP codes are delivery routes, not areas, and the two do not always match.
Some ZIP codes have no ZCTA at all. PO box ZIPs, ZIPs for a single building or a single large organisation, and military ZIPs usually have no area of their own, so they cannot be split across counties here and will not match any area in a map.
Land share is not population share. A ZCTA with 20% of its land in a second county might have almost none of its people there, or most of them. The shares here measure area, which is what the Census file publishes.
Tiny overlaps are included. A ZCTA counts as overlapping a county if the Census file lists any part of it there, including slivers along a road or river. That is why the share with at least 5% of land in a second county is shown alongside.

Source: U.S. Census Bureau, 2020 ZCTA to County relationship file, public domain. Counts use 2020 ZCTAs and 2020 county boundaries. ZIP codes added by USPS since then are not in it, and Connecticut's counties have since been replaced by planning regions in Census data.

Route by the boundary, not the ZIP

MapLogics decides who owns an address from a boundary you draw or import, so a ZIP that straddles two counties is answered by where the address actually is. There is a free trial if you want to see it on your own addresses.

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