Why two sources can give different areas for the same county

The key idea

Resolve disagreements by matching identity, measurement, vintage, units, and precision before deciding that a figure is wrong.

Two different county-size figures do not by themselves establish that one source is wrong. A useful comparison starts with the geography and measurement behind each number. Follow these checks before replacing a value in your spreadsheet or article.

1. Match the place

County names repeat across states. Use both the name and state, or the five-digit Census GEOID. Preserve leading zeros when importing data. Also check whether the source describes a county, independent city, or another county equivalent.

2. Match land with land

Compare the labels before the digits. “Area” can refer to total area while a neighboring table reports land only. US County Area’s total is the sum of Census-published land and water square miles. This guide works through an example.

3. Check the release year

The Census warns that changes to names, boundaries, and geographic entities can prevent a one-to-one match between releases. Record the vintage alongside the figure. A site updated this year may still quote an older dataset; its webpage update date alone does not establish the measurement year.

4. Compare the precision

A displayed 709.3 square miles can summarize more than one underlying value. Two counties that display the same number can have different square-meter areas. US County Area sorts land rankings by the original integer ALAND field and only rounds for display. The CSV and JSON downloads retain both the original square meters and published square miles.

5. Do not measure an illustration

Our outlines use generalized Census boundaries for readable small maps. The Census describes these shapes as simplified and notes that small features and offshore areas can be omitted. A polygon area computed from a simplified illustration is therefore not a replacement for the Gazetteer figure. Maps on separate county pages are also fitted independently; their screen sizes do not compare land areas.

Keep a useful audit trail

Save the GEOID, field name, source URL, vintage, units, and rounding convention. If two figures still disagree after those checks, compare the original source records and report the discrepancy with those details. Every county page includes a suggested citation and a link to the source download.

References: Census Gazetteer notes and cartographic boundary description.

A real example of an apparent contradiction: zero water

Falls Church city has 32 square meters of water in the original AWATER field, but 0 square miles in the published water field. The square-mile value has been rounded. Both values can faithfully reproduce different source fields.

This is why “zero water” needs interpretation. If your question is whether the source records any water at all, inspect the original square meters. If your question is how to reproduce a published square-mile table, use that published field and its precision. A conversion of a rounded zero remains zero; adding decimal places to the display will not restore the missing detail.

A rank can change even when the county’s measurement does not

Rank depends on all the other included records. Excluding Alaska, removing Puerto Rico, restricting to one state, or filtering to a particular jurisdiction type can move a county’s position without changing its area. Comparing ranks from two sources therefore requires comparing their coverage as carefully as their units.

Tie handling is another difference. A source may assign the same rank to exact ties; this site assigns a sequential position after sorting ties by GEOID. Two counties that merely display the same rounded figure are not necessarily tied in the original measurement. Look at the precise source field before treating a ranking difference as an error.

Turn a disagreement into a useful correction report

Save the two values exactly as published, including units and labels. Record both source URLs and the date you accessed them. Add the county GEOID, the stated release years, and the field names where available. Then write which checks you have already completed: same place, same land-versus-total definition, same units, and compatible geography.

If one source lacks a vintage or measurement definition, report that uncertainty instead of assuming one. If the numbers still disagree, the resulting evidence gives the publisher a concrete issue to investigate. The correction instructions explain what to send. A reproducible discrepancy is much easier to resolve than an isolated statement that a county “looks too big.”

Sources and calculation notes

County examples and calculations use our pinned 2026 Census Gazetteer dataset. Ratios use published square-mile values; land rankings use original square meters. Examples labeled hypothetical are teaching examples, not population estimates.

How we calculate and verify the data · Download and reproduce the examples · Suggest a correction