https://dduane.tumblr.com/post/788532027024621568
This is (a) a good question, and (b) one of those Almost Impossible To Answer ones, without getting into some detail.
First of all: "A finished outline" of what? Short story? (And yes, you can outine short stories. Sometimes they need it as much as the longer forms. Or even more.) Novella? Novelette? Novel?
...As your question gets into books later on, let's assume you mean a novel.
As is so often the case, my own experience is going to be a crap example for anyone else, as I am generally the Outlier's Outlier.
My first novel gestated in fits and spurts (with fit-and-spurt outlining) for 10+ years before yelling in my ear OKAY, READY NOW! and pulling me under the surface to drown or swim. Six weeks from (finally completed) outline to completed first draft. (That being the one that sold.)
After that I learned how to really outline from my story editors at Hanna-Barbera... because there is no pantsing in TV: your producers have to know what you're turning in, so they can tell the backers/investors. Pretty quickly I learned the art of (as we call it in the household) "weighing the story in your hand," as if it was a bag of sugar. Is there enough story here to sustain a novel? A novella? A short story? That story must shoulder up under the scaffolding you build for it and have enough power to support the weight of the narrative and the characters' interwoven interactions.
You make your call on this, and then you find outâby trial and errorâwhether you were right or not. Sooner or later you learn whether, and when, to trust your instincts in this regard.
Once you know the number of words you're going to have to work toward... then you can start estimating completion times.
And here is where you learn the hard, bitter business of being honest with yourself. At the end of the day, it comes down to accurate prediction/appraisal of output. How many words are you going to write per week? (I've stopped saying "per day." Too many of the You Must Write X Words Per Day folks have turned this trope toxic, and freaked new writers out.)
But more to the point: can you trust your own estimates?
Let's leave that issue to one side for the moment, and take The Door Into Shadow as an example.
I was just getting to grips with outlining as a necessity at that point (as Deep Wizardry had required something similar). DW was its own set of problems, as the pace of the outlining was being influenced by needing to do real-world research at NYPL (For this was sooooo long before Google, and there was nowhere to get the data I needed except out of books.)
TDISha, though, was another kettle of fish. Beginning and ending were plain enough to me from even the earliest conceptual stages. The middle (as always for me: middles always seem murkiest...) was still up in the air, both structurally and in terms of the intrapersonal relationships that would define it. And the middle had some extremely difficult stuff for the protagoniste to get through. (Disclosure for those who might have heard some whispered stuff about this: in this book, I was working through my own historical sexual assault/abuse at age sixteen by a "friend of the family". Last I heard, adults were still allowed to do this kind of working-through in prose. Got other opinions? I've heard them many times over many years. This approach worked for me.)
Outlining on TDISha took me something like three months. Writing the book took six months, plus/minus... once I was clear that the outline was right on the money and needed to go where it was going. Then I got back to Young Wizards work, and Scooby-Doo. (Or was it Space Ghost by then? I lose track.)
Since then, on every book I've written, outlining has routinely taken six to eight weeks. The books themselves have taken...
...ALL kinds of lengths of time. Outlining of My Enemy, My Ally took about two months. Writing the book (on very short notice, as the publisher suddenly had an empty slot to fill) took eleven days. ("Can you do this?" said the agent over the phone, very concerned. "Are you sure??" I was sure. Because the outline was detailed, even for me, and I knew exactly where I was going.)
Outlining of The Romulan Way, by comparison, took maybe a month, and the book itself took sixteen or eighteen days... because @petermorwood was co-writing. (But he was so intuitive and quick on the uptake that he might as well have been inside my head... and people still have trouble telling which of us wrote what. Which is exactly as it should be, when you're writing as a team. You don't want to be told apart: you're working as a corporate being.)
Yet Tales of the Five: The Librarian, which I'm working on completing at the moment, took maybe a year to outline, and has been drafting since 2019. And many books between now and [twenty? thirty?....) years past, have produced wildly different results that are resistant to any kind of logical analysis.
...I think what I'm getting down to here is that attempts to jam your work-in-progress into a Box of Timing Expectations are possibly futile. All kinds of things will affect your ratio of outlining-to-execution time: life-crisis crap, the annoying intersection of mundane work-and-living needs with creative time, illness, straightforward inability to concentrate on the writing no matter how you try: you name it. It'll just be maddening if you try to force it to make sense. (Especially since so much in this equation rests on how many words you turn out a week. (Month. Whatever. Stop counting it by the day like calories, ffs. Art will not willingly be sliced up to go onto the scale and be weighed by the goddamn gram.)
âŚMy take on this: Stop paying attention to other people's half-baked, self-centered expectations on how fast you should be writing. Do what YOU, and your Work, need to be doing.)
In particular: take the time to do what your story seems to be requiring you to do. And cut it some slack. It may know better than your Conscious Brain does.
More could be said about this, but for the moment, I suspect this is enough. Other people are all too willing to flourish the whip over your sweating, straining Creative Selves' backs and crack it as if your Steeds of Creativity aren't working hard enough to suit their standards.
You know what? Fuck that noise.
"Realistic estimates"? There aren't any. Other people are making them up. They want to make themselves feel right. Whether that makes you feel ineffective is the last thing on their minds. (And work executed from that POV is dreadfully revelatory of their workâs likely quality.)
Work as your own version of the Work desires you to. Write your best at your own best pace.
Those other guys? What have they written lately? Who cares! The hell with them. Go where your own Work takes you, at your (and its!) own speed. Which is the right speed.
And gods' speed. :)
ETA to @rabidbehemoth: Jeez, be SLOW and shame the Devil. Let James Joyce be your poster boy on this! I'm sure he'd have liked to be done with Ulysses sooner, but some things can't be rushed, y'know? :)
https://dduane.tumblr.com/post/788532027024621568