Say that your query letter has piqued the interest of an agent. She wants to see a synopsis, but doesn’t specify how long it should be.
How do you decide? (For some reason you can’t just phone her and ask.)
You can search the web for a nice simple answer.
You’ll get answers, but none will be simple.
Most synopses are one or two pages long at most and give the reader a basic idea for what the book is about.
Suggested length of synopsis, according to Wood: ten to twenty-five pages (each chapter one to three pages).
Then there is this one that covers all bases:
One guideline is to allow one synopsis page for every twenty-five pages of manuscript…Most editors and agents…prefer short synopses — two to ten pages. The busier ones like five pages at most. I personally consider two pages ideal, and have distilled synopses down to a single tight page.
Instead of worrying about length, it may be more useful to think about content.
A synopsis is a sales tool. Its purpose is to persuade an agent or editor that your novel is worth a further look.
Write the synopsis in present tense. Ex. Charlie Jones is a personable young man with a third eye he keeps covered with a patch….
Think book jacket blurb. The synopsis should make the agent want to read the book. NOTE: If your novel is a mystery, don’t hide the ending. The synopsis should give all the information the agent needs to know that the plot structure is solid.
Take pains. The synopsis, even a one-pager, reveals your writing ability.
Focus on important things. Include the main conflict/s, plot turns, and final resolution of the main conflict. Focus on your main characte. Subplots and secondary characters may be mentioned in passing, but keep character names to a minimum. When you do name a character, accompany the name with a few descriptors. Anything else is irrelevant.
Keep it brief. If the person you’re writing the synopsis for hasn’t specified length, short is better than long.
Here’s a link to a TCM “full synopsis” of a film called Send Me No Flowers. It gets the job done in about 280 words, a little more than one typed page.