The short answer
At 800 words per hour and 8 hours a week, an 80,000-word book needs about 12.5 weeks of drafting plus a 4-week editing buffer, which comes to roughly 16.5 weeks from first chapter to revised manuscript. That is the whole idea of this page: pace multiplied by schedule tells you when the draft ends, and the buffer tells you when the book is actually ready. If you write faster or protect more hours, the total shrinks. If your hours slip or your speed drops, the total stretches. Everything below explains how to measure both inputs honestly so the projection matches your real life.
What this tool does and what it does not do
This calculator projects a full-book finish from four numbers: your drafting speed in words per hour, the hours you write each week, the length of the book in words, and an editing buffer in weeks. It answers one question, which is how many weeks stand between today and a finished, revised manuscript at your current pace. It does not time a single session, it does not judge your prose, and it does not write anything for you. Think of it as a map of the whole trip rather than a stopwatch for one mile.
That distinction matters because a similarly named kind of tool, the session-based writing time calculator, works like a timer: you start it, you write, you stop it, and it reports how long that sitting lasted and how many words you produced. That style is useful for studying today. This page works in the opposite direction. You bring an average speed you already measured, plus the weekly hours you can genuinely repeat, and it stretches those facts across the entire manuscript, editing included. Use the timer to learn your speed; use this page to plan your year.
The four inputs, one by one
Words per hour means new draft words produced during sixty minutes of actual drafting. It does not include outlining, research, email, revising yesterday's pages, formatting, or staring at the screen. The default is 800, which sits in the middle of the common range for fiction drafting. Your own number may be far from that default, and that is normal. The tool is only as honest as this entry, so measuring it once with a clock beats guessing.
Hours per week means writing sessions you can repeat in an ordinary week, not a holiday week or a week when someone else handles dinner every night. The default is 8, which could be four evenings of two hours, or two weekend mornings of four hours, or any pattern that survives contact with your job and family. Count only drafting and revising time, not commuting with audiobooks or thinking in the shower. Optimism here is the most common reason projections fail.
Book length in words is the target size of the complete first draft. The default is 80,000, a standard adult novel length. Shorter targets finish sooner in exact proportion: halve the length and you halve the drafting weeks at the same pace. Longer targets stretch the same way. Pick the length your category expects, which the genre section below covers in detail, rather than the length you wish the book were.
Editing buffer in weeks is calendar time reserved for revision after the words exist: resting the manuscript, structural passes, line work, beta readers, and proofing. The default is 4. This buffer adds weeks without adding words, which surprises writers who assume typing the final chapter means the book is done. Revision is a separate job with its own duration, so the total projection always reads drafting plus buffer.
How the math works, step by step
The calculation has three stages, and each one is simple division or addition. First, weekly output equals words per hour multiplied by hours per week. Second, drafting weeks equal book length divided by weekly output. Third, total weeks equal drafting weeks plus the editing buffer. Months are total weeks divided by about 4.345, the average number of weeks in a month.
Walk through the defaults. Weekly output is 800 words per hour times 8 hours, which equals 6,400 words per week. Drafting weeks are 80,000 words divided by 6,400 words per week, which equals 12.5 weeks. Total weeks are 12.5 plus the 4-week buffer, which equals 16.5 weeks. Total months are 16.5 divided by 4.345, which is about 3.8 months. So the default writer finishes drafting around the three-month mark and holds a revised manuscript before the fourth month ends, assuming every planned hour actually happens.
Now change one lever to see how sensitive the result is. Keep speed at 800 and the book at 80,000, but cut hours from 8 to 4 per week. Weekly output falls to 3,200 words. Drafting weeks rise to 25. Total time becomes 29 weeks with the same buffer, or about 6.7 months. Halving the schedule more than doubled nothing; it exactly doubled drafting time, and the fixed buffer rode along unchanged. This is why part-time writers feel progress is slow even when their hourly speed is respectable: the multiplier is small, not the engine.
Change the other lever instead. Keep 8 hours a week and the 80,000-word target, but raise speed from 800 to 1,200 words per hour. Weekly output becomes 9,600 words. Drafting weeks fall to about 8.3. Total time becomes about 12.3 weeks with the buffer, or roughly 2.8 months. Four hundred extra words per hour saved a little over four drafting weeks here. Notice that the buffer did not shrink: faster drafting does not automatically mean faster revising, and sprint prose sometimes needs more revision rather than less.
Try a longer book to complete the picture. A 120,000-word fantasy draft at 800 words per hour and 8 hours a week produces the same 6,400 weekly words, but drafting needs 18.75 weeks, and a 6-week buffer brings the total to 24.75 weeks, or about 5.7 months. Same writer, same discipline, half again as much calendar, purely because the target grew. Length is a lever exactly as powerful as speed or hours, and it is the one writers choose earliest and revisit least.
Reading the what-if table
Below the main result, the tool shows a small table with three rows: the same book and schedule computed at 600, 800, and 1,200 words per hour. At the default 8 hours and 80,000 words with a 4-week buffer, those rows read about 16.7 weeks of drafting and 20.7 total at 600; 12.5 and 16.5 at 800; 8.3 and 12.3 at 1,200. The table exists so you can compare levers without retyping anything. If the gap between your row and the next row up looks life-changing, speed training may be worth it. If the gap looks small next to what two extra weekly hours would do, protect the hours first.
Recompute the table mentally for your own schedule, because the printed defaults assume 8 hours. At 5 hours a week on the same 80,000-word book, the three drafting rows become about 26.7, 20, and 13.3 weeks, each plus your buffer. At 15 hours a week they become about 8.9, 6.7, and 4.4 weeks plus buffer. The pattern never changes: hours scale every row at once, while speed moves you between rows. Writers short on time should therefore read the table down the hours axis first and across the speed axis second.
Pace tiers are conventions, not grades
The tool labels your speed with a tier: Reflective below 400 words per hour, Steady from 400 to just under 800, Brisk from 800 through 1,200, and Sprint above 1,200. These bands are craft conventions, meaning working writers and teachers use them as shorthand for describing pace, not as certificates of talent. A reflective pace often belongs to careful stylists, literary novelists, and anyone drafting difficult material. A sprint pace often belongs to dictated drafts, heavily outlined genre fiction, or fast recreational writing that will lose a share of its words in revision.
Nothing about a lower tier predicts a worse book. Some of the most durable novels were drafted slowly and revised lightly, while some of the fastest drafts were cut nearly in half. The tier helps you interpret the projection: reflective writers should plan longer drafting phases without shame and shorter revision buffers if their prose arrives clean, while sprint writers should do the reverse and reserve extra buffer for structural repair. Speed describes throughput, never worth.
Illustrative example one: the evening writer with a thriller
Consider an illustrative hypothetical writer, Maya, who drafts a 90,000-word thriller after work. She timed three separate one-hour sessions and produced 690, 740, and 710 words, so she enters 700 words per hour. She can protect five evenings of ninety minutes, which is 7.5 hours a week, and she rounds down to 7 to leave margin. She sets a 4-week editing buffer because thrillers need at least one plot-logic pass and one pace pass.
Her weekly output is 700 times 7, or 4,900 words. Drafting needs 90,000 divided by 4,900, which is about 18.4 weeks. Total time is about 22.4 weeks with the buffer, or roughly 5.2 months. The projection tells her something practical: at this pace she cannot draft and revise a thriller between September and December, but she can between September and mid-February. She has two honest options, which are adding a Saturday session of three hours to reach 10 weekly hours and cut drafting to about 12.9 weeks, or accepting the longer arc and planning revision around the holidays. Both beat discovering the shortfall in November.
Hypothetical example two: the weekend writer with a memoir
Consider a second hypothetical case, Daniel, who writes memoir on weekends at a reflective 350 words per hour. His material is emotionally demanding, so his prose arrives slowly and needs fewer structural surprises later. He writes two four-hour blocks each weekend, which is 8 hours a week, toward a 70,000-word manuscript, with a 5-week buffer that includes rest time and two beta readers.
His weekly output is 350 times 8, or 2,800 words. Drafting needs 70,000 divided by 2,800, which is exactly 25 weeks. Total time is 30 weeks, or about 6.9 months. The tier label reads Reflective, and here is where the convention proves its value: nobody should tell Daniel to triple his speed, because his pace matches his material and his revision load will be lighter than a sprinter's. His better lever is length discipline, holding the memoir near 70,000 rather than letting it sprawl toward 100,000, which would add nearly 11 drafting weeks at his pace. The tool does not hurry him; it protects his plan from wishful totals.
Measuring your real words per hour
Guessing speed is the fastest way to waste this tool. Measure instead, and the procedure takes one week. Pick three ordinary sessions of at least forty-five minutes each, on different days, with your usual setup. Draft new material only; do not count sessions spent outlining, researching, or revising. When each session ends, divide new words by session hours including pauses under five minutes, and average the three results. Round to the nearest fifty. That average is your entry.
Several details make the measurement fair. Measure scenes of average difficulty, not the thrilling climax you have awaited for months and not the bridge chapter you dread. Write at your usual time of day, because morning writers measured at midnight produce numbers that never repeat. Keep your phone where it normally sits, because airplane mode produces a laboratory number your life will not sustain. If you dictate, measure dictated hours separately from typed hours, since the two speeds can differ by a factor of two and mixing them poisons the average.
Repeat the measurement twice a year. Speed changes as craft grows, tools change, outlining habits deepen, and life shifts. A writer who measured 500 words per hour as a beginner may reach 900 within two years of steady practice, which cuts every future projection by more than forty percent. Conversely, a writer moving from simple commercial premises to intricate multi-viewpoint structures may slow down while writing better books. Update the entry and let the plan follow the worker you are now.
Counting hours you will actually keep
Hours per week deserves the same realism. Open your calendar and block candidate sessions for the next month, then subtract everything that historically cancels them: late meetings, school events, illness, travel, deadlines in the day job. What remains is your entry. Most writers discover a gap between imagined and protected hours of thirty to fifty percent, which explains why so many projections feel optimistic. The tool multiplies whatever you type across every week of the draft, so a two-hour fiction compounds into dozens of missing hours by the end.
Design the week so the hours survive. Shorter sessions kept consistently beat heroic sessions that collapse: four mornings of ninety minutes outproduce one Sunday marathon that gets bumped by family plans, and they keep the story warm between sittings, which protects speed itself. Attach sessions to existing anchors, such as writing from seven to eight before the household wakes, rather than floating them wherever time appears. Track kept versus planned hours for a fortnight; if you keep six of eight, enter six and treat the extra two as bonus weeks that pull the finish closer.
Missed weeks need a policy before they happen. One lost week at 6,400 weekly words adds a full week to drafting, plus a small restart cost while you reread and re-enter the story. Two lost weeks in a 12.5-week draft push the finish nearly twenty percent. Decide in advance that a missed session moves to a defined makeup slot within seven days or the plan extends by exactly that amount with no guilt and no fantasy catch-up math. The projection stays trustworthy only when slippage is recorded instead of absorbed silently.
Choosing the editing buffer with intent
The buffer is not padding; it is the second half of the job, itemized. A minimal 2-week buffer suits short category fiction with light revision: one week of rest and structural review, one week of line polish and proofing. The 4-week default suits a standard novel: a week of rest, a structural pass, a scene-level pass, and a final proof with early reader feedback folded in. Long, intricate, or debut manuscripts often need 6 to 8 weeks, especially with beta readers whose turnaround you do not control.
Match the buffer to revision history, not hope. If your last book lost fifteen percent of its words between first and final draft, your next book at sprint speed deserves at least 5 weeks. If your critique group needs three weeks to return chapters, that waiting time belongs inside the buffer even though you are not typing. If you plan professional editing, ask the editor's lead time and add it after your own passes rather than inside them. Writers who compress the buffer to make the total attractive usually borrow those weeks back later at higher stress.
Rest time counts as work inside the buffer. A manuscript set aside for ten to fourteen days returns with visible flaws that fresh eyes cannot see on day one, which makes the subsequent passes shorter and sharper. Cutting rest to save two weeks often costs three in confused revision. Enter the rest honestly and let the total reflect a process that actually improves the book.
Genre-specific guidance
Romance rewards speed within a narrow length band. Category romance runs about 50,000 to 60,000 words, and single-title contemporary romance runs about 75,000 to 90,000. At 800 words per hour and 8 hours a week, the category length drafts in roughly 7.8 to 9.4 weeks, while single-title needs about 11.7 to 14 weeks, each plus a 3 to 4-week buffer for beat checks and heat calibration. Series romance writers should compute per-book time and then multiply across the contracted books, because three 60,000-word books at this pace need roughly 28 drafting weeks before any buffer, which surprises authors who think in single titles.
Mystery, thriller, and suspense cluster near 80,000 to 95,000 words with revision-heavy buffers. Drafting pace for this group often lands in the Steady to Brisk range, but plotting constraints slow many writers: fair-play clues, timelines, and suspect management demand outlining that the hourly speed does not capture. Enter your true drafting speed excluding outlining, and hold a 4 to 5-week buffer for logic passes. A thriller writer at 700 words per hour and 7 hours a week on 90,000 words should expect about 18.4 drafting weeks plus buffer, as Maya's sketch showed, and should resist shortening the buffer because the genre punishes logic errors hardest.
Fantasy and science fiction run longest and slowest per hour. Epic fantasy commonly spans 110,000 to 150,000 words, sometimes more, while science fiction clusters near 90,000 to 120,000. Worldbuilding decisions, invented terminology, and multi-thread plots reduce effective speed even for experienced writers, so measure during representative chapters rather than fast dialogue stretches. At 700 words per hour and 8 hours a week, a 130,000-word epic needs about 23.2 drafting weeks plus a 6-week buffer for continuity passes, or roughly 6.7 months. Plan length cuts early: every 10,000 words removed saves nearly two drafting weeks at that pace.
Shorter forms need adapted use. Memoir and narrative nonfiction often run 65,000 to 90,000 words with research drag from interviews and fact-checking, so measure drafting hours alone and carry research in a separate block outside this tool. Prescriptive nonfiction at 40,000 to 65,000 words often drafts fastest because chapters transfer from existing talks, but freeze the table of contents first since each added chapter costs about two drafting weeks. Picture books, poetry, and essays break the hourly model entirely; for those, enter an effective speed that reproduces your last comparable finish and use the tool as a calendar divider.
Edge cases and failure modes
Zero-hour weeks break every projection silently. Vacations, illness, school breaks, and crunch periods at work do not merely pause the draft; they add re-entry cost on return. A two-week gap in the middle of a 12-week draft typically costs two weeks plus two to four sessions of rereading and warming up. If your year contains predictable dead zones, subtract them from the plan explicitly: compute drafting weeks, then add known dark weeks on top, rather than pretending an average absorbs them.
Speed measured on easy chapters fails on hard ones. Openings, climaxes, and chapters with new viewpoints, technical exposition, or emotional confrontation routinely run twenty to forty percent slower than connective scenes. A writer who measured 1,000 words per hour on banter and applies it to a battle-heavy finale will miss by weeks on a long book. Measure across a representative mix, and if the remaining chapters are known-hard, reduce the entered speed by a quarter for the rest of the projection.
Dictation creates a two-speed problem. Many writers dictate at 1,500 to 2,500 words per hour but revise dictation more heavily than typed prose, with cleanup of homophones, punctuation, run-ons, and repeated phrasing. Entering raw dictation speed with a standard buffer understates total time. The fix is net speed: track finished words surviving into the second draft per dictation hour across two weeks, and enter that net figure. If gross is 2,000 and a third is cut or rewritten, the honest entry is about 1,300.
Heavy outliners face the mirror problem. An author who spends forty hours structuring before drafting will show a dazzling drafting speed, perhaps 1,200 words per hour, because decisions were prepaid. The projection then looks short while total project time is long. Account for outlining outside the tool or amortize it: divide outlining hours by expected drafting hours and reduce entered speed proportionally, or add the outlining weeks to the buffer. Either keeps the total honest.
Collaboration, illness, and caregiving change hours more than speed. A co-written book does not usually double weekly output, because coordination, voice matching, and handoff friction consume a share of both partners' time. Enter combined net weekly words from a trial fortnight rather than summing two individual speeds. Similarly, writers managing health or caregiving should enter the minimum reliable hours rather than the average, so good weeks pull the finish closer instead of bad weeks pushing it away.
Very short books expose fixed costs the tool does not model. A 15,000-word novella at 800 words per hour and 8 hours a week computes to under three drafting weeks, yet cover design, formatting, and publication steps still consume calendar months. Very long books expose the opposite: fatigue, continuity drift, and middle-book slowdowns that a flat average hides. Treat projections beyond about nine drafting months as planning brackets with a twenty percent contingency rather than promises.
Perfectionism masquerading as speed is the quietest failure. Writers who revise each paragraph before advancing report low hourly speeds but need small buffers, while writers who push forward carelessly report high speeds and need large ones. Both are consistent if buffer matches style. Trouble arrives when a slow, careful drafter also reserves a huge buffer, double-counting caution, or when a fast, loose drafter reserves none. Align the two entries with your temperament: careful drafters earn shorter buffers, sprinters owe longer ones.
Which lever should you pull
Three levers move the total: speed, hours, and length. Their power differs by situation, and the tool lets you test each in seconds. Adding 200 words per hour at the default book and schedule saves about 2.5 weeks of drafting. Adding 2 hours a week at default speed saves about 2.5 weeks as well. Cutting 10,000 words saves about 1.6 drafting weeks at default pace. None dominates universally; the cheapest weeks come from whichever lever you can move without breaking quality or life.
For most part-time writers, hours dominate. Raising a thin 3-hour week to 5 hours cuts drafting time by forty percent at unchanged speed, with zero risk to prose. For full-time writers already near twenty hours, further hours risk burnout and speed work pays better: moving from 800 to 1,000 words per hour at 20 hours a week saves about 2 drafting weeks on an 80,000-word book. For overwriters, length dominates everything: a 120,000-word draft cut to 100,000 before writing saves more than any plausible speed gain.
Speed training itself deserves realistic expectations. Timed sprints, scene-level outlining before sessions, dictation for first passes, and separating drafting from editing can lift many writers from Steady into Brisk over a season. Gains beyond Brisk usually require structural changes like full outlines or dictation rather than effort alone, and they often raise revision load. Test any new method for a fortnight, measure net surviving words per hour, and only then update the projection. Permanent gains compound across every future book; temporary sprint highs do not.
Planning the weeks, not just counting them
A projection becomes a plan when hours turn into named sessions. Divide weekly hours into two to five sittings, since single weekly marathons stall while the story cools and daily fragments under forty-five minutes lose too much to warm-up. Convert drafting weeks into chapter milestones: an 80,000-word book in 20 chapters at 6,400 weekly words completes about 1.6 chapters per week, so each fortnight should deliver roughly three. Schedule the buffer on the calendar now with labels for rest, structural pass, reader window, and final proof, because an unscheduled buffer evaporates and the 16.5-week book quietly becomes a 24-week one with no decision ever taken.
Common questions writers ask next
How accurate is this projection for a first novel. It is accurate the way a budget is accurate: exact arithmetic on estimated inputs. The division never errs, but first-time speed and hours estimates often do, usually by twenty to forty percent. Treat a first-book projection as a bracket: compute the total, then also compute it with twenty percent fewer hours, and plan your commitments around the longer figure. After one finished draft you will own real numbers and the second projection will be close.
What if my speed varies wildly between sessions. Enter the average of representative sessions and let the buffer absorb the variance, or enter the lower quartile if deadlines are fixed and optimism is expensive. A writer alternating 400-word and 1,200-word hours averages 800 only if the mix stays even; if hard chapters dominate the remaining work, weight the entry toward the slower figure. The tool assumes a flat pace, so feed it the pace of the road ahead, not the road behind.
Should outlining hours count inside words per hour. No. Keep outlining separate, because mixing planning time into drafting speed understates pace and then double-counts planning inside the buffer. Measure drafting speed during drafting, estimate outlining as its own block of weeks, and add that block alongside the editing buffer when you calendar the project. Writers with forty-hour outlines and fast drafting look slow only when the two jobs share one number.
When should I recheck the projection. At the quarter marks: after one quarter of the target words, compare actual calendar weeks against the projected share.
Where drafting happens after planning
Once the projection gives you a week count, the work moves to actual chapters, and that drafting needs a steady home. Co-Writer at the slash write path is the place in this product where new chapters get written, session by session, toward the word target this page just sized. You can carry the weekly word goal from the calculator into those writing sessions and watch each sitting contribute its share. When the projected drafting weeks end, the manuscript waiting there becomes the input to the editing buffer you already scheduled.