Manuscript to book
I've been reading "The Complete Guide to Self-Publishing" by Marilyn Ross & Sue Collier. There are a myriad of great tips, tools and rules that every self-publisher should know. One of these great tools is a formula on how to convert an 8x11 manuscript into a 6x9 book size. (Here is a great article on how to format an 8x11 manuscript.)
In most cases, a 6x9 book is about one and one fourth (1.25) pages of a double-spaced manuscript in 12 point Times New Roman with 1-inch margins. Let's say your manuscript is 285 pages long, divide the number of pages by the 1.25 ratio, and the result indicates you will have 228 typeset text pages.
Remember, the final number of pages you calculate out may be different than the final 6x9 printing due to changing in the set up and typeset layout. But, it is nice to have an idea what size your book will be.