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Calcite | Level 5

Purpose: How to calculate the ZCTA radius within a ZCTA?

Background: I have two groups of nodes: from and to. The two groups may locate in the same ZCTA (25%) but most of them had different ZCTAs (75%). I managed to calculate the ZCTAs distance for the 75%, centroid to centroid. But I don't know how to assign a distance to the other 25%. I expect to use ZCTA radius as a proxy for that purpose. Can anyone help me with it? Thank you in advance!

BTW, 5-digit zip code is the only available geographic info.

Lapis Lazuli | Level 10

Hi adcc5460,

You can find a ZCTA table with square mileage A (area) for each ZCTA, see this website

Based on this table you can calculate a ZCTA radius R from A=πR2, then R=(A/π)1/2.


You can also look into getting an average distance between two points within a circle, see


Hope this helps.


P.S. For some reason superscripted 2 and 1/2 came out as subscripted 2 and 1/2.

Calcite | Level 5


Thank you!

Is there any supporting evidence to treat a ZCTA as a circle to do that?



Lapis Lazuli | Level 10

Hi Kevin, I was just answering your question "How to calculate ZCTA radius?" - What other than circle has a radius? 🙂


Lacking information about the ZCTA shape, circle seems as a reasonable approximation.


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