How is the estimated fill-factor percentage related to the size of a database?

When you rebuild an index first the new index is built and only then the old index is dropped. And if you don't use

  SORT_IN_TEMPDB = ON

the space that the server needs to make a sort is allocated within your DB Your DB has now empty space, it's not space reserved for any object, it's just free space (space that was freed after temp objects needed to do sort were dropped) So your indexes are not empty on 42%, it's your DB that is empty on 42% and if you do shrink a data file (I don't recommend it) your DB will occupy only 82Gb Best Value for fill factor in SQL Server In short, the bigger the fill factor, the smaller the disk footprint of the index and vice versa. In the end, it will advise planning the indexes and the fill factor. This tip will focus on how to plan for an appropriate fill factor by analyzing the impact of different fill factor numbers and by studying a few facts about the data in the index columns.