The short answer is it should take around 100 hours to finish your first draft. And when I say around, I mean it could take you anywhere from 50 to literally infinite hours, depending on how you write and how disciplined you are.
How did I come up with 100 hours? I'll show you:
I've been recording my numbers (I'll edit in the numbers later, once I figure out how to put them into an attractive state) from these sprints I've been writing lately.
What are Writing Sprints?
On average, I'm hitting around 400-600 words on every 30 minute sprint. Taking the conservative estimate, I can say that I write 1000 words per hour. If you are aiming for 100,000 words on your book, well, the math is pretty easy.
100,000 words / 1000 words per hour = 100 hours to write a first draft
I have to be honest:
There are 10,000,000+ factors that will change how long it takes you to finish editing and put the words "Final Draft" onto your novel.
By the time some authors end up finishing their book, they end up rewriting up to 90% of their first draft. There is even a legend that one author* only edits as he writes, and when he finishes the book, it's DONE.
The time it takes to start and finish a book will also vary on 10 million things: how fast you write, your discipline, your editing proficiency, etc. The general consensus, especially for first time writers, seems to be this - it takes at least one year, usually up to three to finish your first novel.
Let's assume you're not writing the next War and Peace (Tolstoy wrote this mammoth novel between 1862 and 1869). You can probably aim between two and three years as a realistic goal for your novel. One year, if you're infected by the ferocious writing bug.
You can probably aim between two and three years as a realistic goal for your novel.
*If you know the Author who I'm talking about, please tell me who in the comments, as I've forgotten if I'm making up this legend or not.
The thunder of water drowns out all other sounds, and when your guide speaks, you can not hear him. His lips open and close like a mute fish gasping for air. Torrential rains shower down on you, and the sound of rush of the waterfall seems to crush the very air in front of you.
You crane your head upward, scoping out the wet, jagged face of the cliff. Shielding your eyes with both hands, you look up. The spray of the waterfall shreds itself against the rocks that jut out, turning into a fine, white mist that rises in clouds.
Your guide points to a ladder bolted into the cliff face. It's tucked behind the waterfall so that only the spray, and not the head-hammering force of the water reaches it.
The ladder's metal shines slick and slippery in the sunlight, and it's rusted metal handholds look more tried than true.
Your guide leans into your ear, and shouts, "This is it! This is the beginning!"
"Beginning of what?"
"Your book, obviously!"
"What are you talking about?"
He pulls you in close again, "Each one of those rungs is a single sentence. If you want to finish your first draft, you must climb, one rung at a time. Try not to reclimb too many rungs, you will slow and wear yourself out."
You tilt your head further back, trying to find a point where the ladders end. All you see is the white mist of the waterfall, boiling and billowing above.
"What's at the top?"
Your guide shrugs, "Only one way to find out!"
Start Your Climb: Pull out that old manuscript, or start a new one. Set a timer for 30 minutes. Focus on exploring the single most obvious part of your story. Have you had a character stuck in your head for the last week? Have you always wanted to write that alternate history?
Write. Do not rush yourself. Go at your normal pace - this is not a race to see how many words you can write. It's a marathon to see how well you can tell a story. Discover your pace.
Related: Afraid of Writing? Me Too