Leesee ....
You got some unknowns and you got some guesstimates.
1) A positive response from an agent on a query -- a week to four/six months.
Once the qurey is read, it will probably be acted upon within the hour.
You can get an email response -- 'send me the full' -- virtually as soon as your query lands on her desk.
Or an agent might take 4 to 6 months to get around to reading the query.
Let's say 8 to 12 weeks is mid-range on response to the initial query.
2) A positive response from an agent on a submitted full manuscript -- a week to six months.
The turnaround speed on a full manuscript can be very short -- ten days or a week. That means the agent kept an eye out for it and read it at once.
Turnaround can also legitimately take six months. Agents have six-foot stacks of mss and yours may go on the bottom instead of the top.
The determining factor on this step is how soon the agent reads it.
A decision to represent or not represent is probably made in a day or two, at most, after the ms is read.
Do not give long exclusives on your manuscripts.
3) The agent works to improve the ms. --- zero to six months.
Some agents require authors rework mss extensively before they submit them. Some agents don't touch mss at all the slightest bit.
4) The agent sends her query to the publishers --- call it a week.
This process starts more or less immediately after the agent is satisfied with the ms. She'll have to acquired any bio or other information she needs from the author, but basically, once she has the manuscript in her hot little hand, she can start querying it.
5) The editor responds to the agent's query and asks to see the full. -- Two weeks.
This should happen rather quickly. If your agent is a good one (and why would you sign with a bad agent?) she will get positive editor responses within two weeks on virtually all her queries.
6) The editor reads the manuscript. -- one to six weeks.
A full manuscript submitted by a trusted agent should land on the top of the editor's pile. Editors are busy people, but there should be only a few mss in line before yours.
The length of this step is why you get a good agent.
With a good agent who has a stable of good writers and who brings editors the manuscripts they want, the lag before reading will be as short as the editor can make it.
If the 'agent' is unknown, the ms he submits goes to the bottom of the pile. Six months ... eight months ...
7) The editor sells the manuscript to the publishing house committee. -- 2 months for this.
Your agent may hear the manuscript is under serious consideration much more quickly.
Here, the in-house acquisition process moves forward, with your future editor fighting to get your manuscript approved. The process involves many people who must read the manuscript. And a committee meet-thing.
8) The manuscript is acquired and the contract is signed. -- A week to 3 months.
And here having an agent slows things down. On your own, you'd sign on the dotted line. Your agent takes a while and negotiates. It is time well spent.
9) The book is edited and printed -- nine months to one year.
After acquisition, the physical process of printing the book is scheduled. This printing date rules the advance of all other activities.
During this year or nine months ...
The title will be determined.
Release date will be set.
The acquiring editor will read and edit the book.
The writer and editor make necessary changes to the ms.
The book is sent to a copyeditor.
The writer approves copyedits.
The art department designs and creates the cover.
Marketing writes the cover copy.
Writer provides bio, pictures and acks page.
The book designer choses font and presentation.
Galleys are printed.
The author does page proofs.
The ARCs are printed and distributed by Publicity.
Minor typos are corrected in the page proofs.
The book is printed.
10) The printed book is sent to stores and put on the shelves. -- 3 months
It's a wonder anything gets published at all.