In order to write, edit and format an index, approximately one week (5 business days) is required for every 250
pages of text.
A very "basic index" (i.e., short and shallow) may take just as long, if not longer to write as a comprehensive index. The "depth" of indexing varies with the page content, the audience and length of the index.
The indexer is involved with many publishers and authors so it is important to schedule with the indexer with adequate lead time.
Editing of the index
Editting takes between 20% to 40% of the total indexing time;
Editting is a vital step, and readers will definitely notice if an index has not
been given enough editing time;
The more consistent and structured the main text is, the less time required
Editting multi-authored works requires more time for editing because of
differences in terminology, writing style and voice.
Factors than can increase the time required to index
Complexity of the text such that a detailed comprehension of the text is
required before indexing can proceed;
Indexing of detailed notes or references;
Requirement for non-standard house style format;
Indexing of figures and tables;
Poor quality page proofs, or awkward size or format that make reading
difficult;
Indexing reference and research text where the index needs to equal in
importance the textual content of the document;
Text with foreign language content;
A poorly edited text;
Changes in page numbering after the indexing process has begun;