Although Google Sheets does not provide a ready-to-use function that takes a column index as an input and returns corresponding letters as output, we can still do the task by leveraging other built-in functions ADDRESS , REGEXEXTRACT , INDEX , SPLIT as shown in the post . However, in form of a formula, that solution is not applicable for scripting with Google Apps Script. In this post, we look at how to write a utility function with Google Apps Script that converts column index into corresponding letters. With the solution in the form of a formula , we don't even need to understand how column index and letters map each other. With apps script, we need to understand the mapping to come up with an algorithm. In a spreadsheet, columns are indexed alphabetically, starting from A. Obviously, the first 26 columns correspond to 26 alphabet characters, A to Z. The next 676 columns ( 26*26 ), from 27th to 702nd, are indexed with 2 letters. [AA, AB, ... AY, AZ], [BA, BB, ... BY, BZ],
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