Nathan Bransford - The Forums

Agents often request a synopsis. Short, medium, Long. One page, two, sometimes five, but this is meaningless information. A double-spaced page in 12-point Times is approximately 250 words. A single-spaced page is twice that.

Agents would be better served (as would authors) by asking for a XXX-word synopsis. We use word count for submissions; why not word count for synopses as well?

I was under the impression only your MS should be double spaced. But who knows...

Formatting and Submitting your Manuscript by Chuck Sambuchino says this

There are no hard and fast rules about the synopsis. In fact, there's conflicting advice about the typical length of a synopsis. Most editors and agents agree, though: the shorter, the better.

and

Formatting Specs

• Use a 1" margin on all sides
• Justify the left margin only.
• The text throughout the synopsis should be double-spaced (unless you inted to keep your synopsis to one or two pages, then single-spaced is okay).

And about 10 other things. It has sample queries, synopsis, cover letters, etc. for different genres. You may want to check your local library for it. Also, the best thing you can do is find out what the specific agent prefers. Most of them will have information posted on their websites to help you out.

I've heard conflicting advice about the spacing. When writing a synopsis I single-space and fit it into a single page, then double-space it before sending it out. However many pages that makes it, so be it (it's usually under three full pages). If the agent wants more, I can expand it. Better to keep it brief in the beginning, though, when your query/synopsis pair is sitting in a pile among hundreds of others.

Author! Author! gave a pretty good and long post on synopsis lengths.

http://www.annemini.com/?p=6947