The Soundex is 4-character code for surnames. It was designed to produce one code for names that may be spelled differently, but have similar sounds. For example, Vose and Voss would have the same soundex code - V200.
All available US Census Indexes from 1880 to the present are cataloged by Soundex, not by surname. To convert your surname to Soundex code, use the first letter of the surname, and substitute the remaining consonants with the number preceding it in the chart:
If your surname has more then the needed letters, disregard them. If your surname has less letters, substitute zero (0) for the remaining spaces. For example: Kensington. K525- you disregard the other letters Example 2: Lee is code L000. There are no codable letters, so use zeroes to make the code 4 characters long.
If your surname has double letters, they should be treated as one letter. For example: McKenna. The second n should not be coded. For Voss, the second s should be not be coded.
Other combinations of letters may be treated as one letter.If your surname has two or more adjacent letters with the same coding number, treat the group as one letter. For example: Fischer. S and C both have 2 for a coding number. You would not code the C, so the Soundex for Fischer would be the same as that of Fisher: F260.
If you still aren't sure how this works try the Rootsweb automated version.