If you put that table in an Access database, it's a trivial task to make a screen with 2 fields (zip_code from, zip_code_to) and a button executing the following query:
SELECT SUM (households) FROM mytable WHERE zipcode>=zip_code_form AND zipcode<=zip_code_to and put the result in a display field (the technique is to the DSUM-function.
But it can be done in Excel also.
http://www.ozgrid.com/Excel/sum-if.htm tells why you can't use SUMIF (because it uses multiple criteria), but gives DSUM as an alternative. That should work.
Dear fellow Numbers Users..
I have a table with zip codes (Column A) and in the same table I have a list of house holds (Column B).
I would like to calculate a sum of house holds based on two fields describing Zip Codes FROM to Zip Codes TO.. I.e. I have a zip code 4000 to 4100. In this range there is maybe 6-7 zip codes with different number of house holds...
I can't figure out how to make that look up and sum.. I have tried to use Sum.if - but apparently I am not clever enough...!
Thank in advance,
Morten (From Denmark... reason for my bad English!)