Three titles selling 120 copies each per month at a $2.45 ebook royalty, with 30 percent of that volume arriving as borrows paying $1.10 each and 15 print copies per title at $3.10 each, reach about $876 a month, which annualises to about $10,508 a year by straight multiplication. That sentence is the entire tool in one breath: monthly income measured from numbers you type, multiplied by 12. Nothing in the result predicts what you will actually earn, because sales move every month and a single multiplication cannot know that. Use the annualised figure the way you would use a speedometer reading extended over a whole trip — it tells you the pace right now, not the traffic ahead.
How the math works, step by step
The tool runs four multiplications and two divisions. Start with monthly volume per title, which defaults to 120 copies. That 120 means ebook copies sold plus borrows taken together, not ebook sales alone. The KU share field, defaulting to 30 percent, splits the 120 into its two parts: 36 borrows and 84 sold copies. Each part then gets its own royalty. The 84 sold copies multiply by the average ebook royalty of $2.45, giving $205.80. The 36 borrows multiply by the $1.10 illustrative borrow payment, giving $39.60. Print sits outside that split entirely: 15 print copies per title multiply by the $3.10 print royalty, giving $46.50.
Add the three rows for one title: $205.80 plus $39.60 plus $46.50 equals $291.90 per title per month. Multiply by the title count of 3 and the monthly total is $875.70. Multiply that monthly total by 12 and the annualised figure is $10,508.40. Divide the annualised figure by 3 and each title carries $3,502.80 per year at the current pace. The comparison table takes that per-title annual number and shows it beside a 20 percent illustrative lift: $3,502.80 becomes $4,203.36, and the three-title total moves from $10,508.40 to $12,610.08. Every royalty and rate in that chain is an illustrative planning assumption you supply or accept from the defaults, so the output is only as honest as the inputs.
Notice what the tool never does. It never looks up your actual store reports. It never adjusts for the month you launched, the price you changed last Tuesday, or the promotion running this weekend. It takes the snapshot you describe and extends it in a straight line. That straight line is useful for sizing decisions — whether a new cover redesign can pay for itself, whether a monthly ad budget fits inside royalty income, whether print is worth keeping in stock — and useless for promising a yearly total. Treat the monthly total as the measured part and the annualised part as the sketch.
What each input means and how to choose it
Number of titles counts the books that genuinely share the pace you enter. Three books each moving roughly 120 copies a month belong together in one run. A series where book one moves 400 copies and book four moves 30 does not belong in one run, because the average hides both ends. Run the fast book and the slow book separately, then add the two monthly totals yourself. Box sets count as one title only if you enter the box set's own volume and royalty, not the sum of the books inside it.
Monthly sales per title means copies plus borrows in an ordinary month. Pick a normal month, not launch month and not a free promotion month. If your last three ordinary months were 100, 130, and 124 copies, enter 118 or 120 rather than the best one. Authors consistently overstate this field by remembering the peak, and every overstatement multiplies by 12 in the annualised row. When in doubt, open your sales reports, take the last full calendar month without a promotion, and type that number.
Average ebook royalty means the dollars you keep per sold copy after the retailer's cut and any delivery fees. A $4.99 ebook on the 70 percent tier, after delivery costs, commonly lands near $3.40, while a $2.99 ebook lands near $2.00. The $2.45 default sits between those points and suits a catalogue with mixed pricing. If every book you sell is priced at $0.99, your royalty is near $0.35 and the default would overstate your income by a wide margin, so replace it. If you sell direct from your own site at higher margins, blend that in: weight each channel's royalty by its share of copies.
KU share means the percentage of monthly volume that arrives as borrows instead of sales. Authors exclusive to one large subscription program often see 40 to 70 percent of volume as borrows, while wide authors see zero. The distinction matters because a borrow pays the flat illustrative $1.10 in this tool while a sale pays your full ebook royalty, so moving share from sales to borrows at the same volume lowers income whenever your ebook royalty sits above $1.10. Set this field from your reports: divide last month's borrows by total volume and round to a whole percent.
Print sales per title and print royalty work the same way as the ebook fields but stay separate because print royalties follow different arithmetic in real life — print costs, wholesale discounts, and expanded distribution all bite before you are paid. The tool does not model any of that. It multiplies the two numbers you enter. Find your per-copy print royalty from your distribution report, which already subtracts printing costs, and enter monthly print copies from a non-holiday month unless holiday gifting genuinely dominates your year.
Illustrative example one: a debut novelist with a single book
Consider a hypothetical debut novelist, used here as an illustrative example only. She has one literary fiction title priced at $4.99, selling 40 ebook copies in a normal month with almost no borrows because she distributes widely. She enters 1 title, 40 monthly copies, a $3.40 royalty, a 10 percent borrow share, 5 print sales, and a $3.10 print royalty. The split gives 36 sold copies and 4 borrows. Ebook income is 36 times $3.40, or $122.40. Borrow income is 4 times $1.10, or $4.40. Print income is 5 times $3.10, or $15.50. The monthly total is $142.30, which annualises to $1,707.60.
Read that result the way the tool intends. The $142.30 monthly pace is the informative part — it says one book at 40 copies covers a modest monthly cost but not a living. The $1,707.60 annualised figure is arithmetic, and this hypothetical author should expect real months to land above and below it as reviews accumulate, prices change, and seasonal reading shifts. The verdict row will flag this pace as modest and point at volume as the lever, which matches the situation: at $3.40 per copy, each additional 10 monthly copies adds $34 a month, or $408 a year at the same pace. The practical question the numbers raise is whether a second book or a sustained promotion schedule can lift monthly volume, not whether $1,707.60 will arrive exactly.
Illustrative example two: a six-book series with heavy borrows
Consider a hypothetical series author, again purely illustrative and not drawn from any real account. He has six mystery titles, all exclusive to a subscription program, each moving about 200 copies of monthly volume at a 60 percent borrow share. His ebooks are priced at $3.99 with a $2.70 royalty, print moves 8 copies per title at $3.10. The per-title split is 120 borrows and 80 sales. Ebook income per title is 80 times $2.70, or $216.00. Borrow income per title is 120 times $1.10, or $132.00. Print per title is 8 times $3.10, or $24.80. Each title pays $372.80 a month. Across six titles the monthly total is $2,236.80, annualising to $26,841.60, or $4,473.60 per title per year.
Two details deserve attention in this hypothetical case. First, borrows contribute $792 a month of the $2,236.80 total — more than a third — so any change to the illustrative $1.10 rate would swing the result noticeably. If the real borrow payment in a given month turns out lower, the author should re-run the tool with adjusted expectations rather than trusting the old output. Second, the 20 percent illustrative growth column shows each title moving from $4,473.60 to $5,368.32 a year, which across six titles is $32,209.92. That column exists to size opportunities — a $500 promotion that plausibly adds sustained volume looks different against a $5,368 upside than against a flat month — and it never promises the lift will happen.
Edge cases that break the estimate
Zero titles produces zeros everywhere, and the tool says so plainly instead of inventing income. Zero monthly volume with titles entered does the same. Both states are starting points, not failures: enter a comparable author's pace or your own first real month when you have it.
A single viral month breaks annualisation completely. If a promotion drove 2,000 copies last month against a normal 150, entering 2,000 annualises a spike into $24,000 of phantom yearly pace. Always enter the normal month and model the spike separately, or run the tool twice — once at the normal pace, once at the promo pace — and weight them yourself across the year.
Price changes mid-year split the year into two regimes. A book that sold 200 copies at $0.99 royalty of $0.35 for six months and then 120 copies at a $2.45 royalty behaves like neither input set for the full year. Run both regimes, annualise each, halve each, and add them. The tool cannot do this blending for you because it holds one royalty per run.
New releases reset every input. A second book does not simply double the first book's volume — it often lifts the first book's volume through series read-through while starting near zero itself. Model the catalogue as it stands today, then model it again a month after the new release with fresh numbers. The comparison between the two runs is more informative than either run alone.
Currency mixing silently corrupts the result. If some royalties arrive in pounds or euros and others in dollars, convert them to one currency before entering anything. The tool multiplies what you type and has no exchange-rate step.
Failure modes to watch for
The most common failure is entering revenue where the tool asks for copies. Typing last month's $400 payout into the monthly copies field produces nonsense, because the tool will multiply $400 by your royalty as though dollars were units. Copies go in copy fields; dollars go in royalty fields.
The second failure is counting borrows twice. If your sales report already folds borrow-equivalents into total units, set the borrow share from that same report's split and do not add extra borrows on top. The tool's split assumes the volume field already contains both parts.
The third failure is forgetting the retailer's cut. Entering the $4.99 list price as the royalty nearly doubles the estimate, since the store keeps roughly a third before you are paid. Royalties are keep-per-copy, never list price.
The fourth failure is reading the growth column as a promise. The plus-20-percent column is labelled illustrative because it assumes volume rises with no cost, no price cut, and no extra effort. Real growth usually costs advertising, newsletter placements, or price promotions, each of which changes the royalties or volume the growth builds on. Use the column to judge whether growth is worth chasing, then budget the chase separately.
Genre-specific guidance
Romance series live on volume and borrows. A romance author with rapid releases may see borrow shares above 60 percent and per-title monthly volume in the hundreds, with modest per-copy royalties from $2.99 pricing. For this genre, run the tool per series rather than per catalogue, because a completed five-book series behaves nothing like a new duet. Pay special attention to the borrow row of the breakdown — in borrow-heavy romance it can exceed the ebook row, which means the illustrative $1.10 assumption carries unusual weight and deserves re-checking against recent payments.
Mystery, thriller, and crime books often split between wide sales and subscription borrows, with steadier backlist volume than most genres. A midlist mystery title selling 80 to 150 copies a month for years is common, and print can contribute a larger share here than in romance because this readership still buys paperbacks. Enter print numbers carefully rather than leaving the default, and consider running one estimate for ebook plus borrows alongside a separate look at print over holiday quarters.
Fantasy and science fiction carry longer books, higher list prices, and stronger series read-through. A $5.99 or $6.99 price point lifts the per-copy royalty toward $4.00, which means each additional monthly copy moves the annualised figure more than the defaults suggest. These genres also reward box sets: model a box set as its own title with its own volume and royalty, since its per-unit economics differ from the individual books.
Nonfiction earns differently. Monthly volume per title is often lower — 20 to 60 copies — but prices run higher, royalties per copy can exceed $5, and print plus direct sales matter more. A nonfiction author should replace every default royalty, because the $2.45 ebook default understates a $9.99 short guide and the $3.10 print default understates a high-margin workbook. Also remember that nonfiction sells on the author's platform, so any quarter with speaking or teaching income layered on top should be tracked outside this tool.
Memoir and literary fiction usually show the thinnest monthly volume and the highest reliance on print and events. If most of your copies move at readings or through local shops, make sure the print royalty you enter reflects what you actually keep after wholesale terms, and treat the annualised figure as the floor that events build on rather than the whole picture.
Children's picture books and heavily illustrated titles need the most caution, because print costs consume most of the list price and ebook volume is typically small. The tool's simple print multiplication can overstate income if you enter list price minus a guess instead of the true per-copy royalty from your statements. Pull the real number first.
Reading each output block
The verdict row gives the headline: monthly total, annualised total, and title count in one line, plus a sentence that names the pace as arithmetic rather than prediction. A strong pace earns a passing note, a thin pace earns a warning that names volume as the lever, and empty inputs earn a neutral note telling you what to enter first. Read the verdict as triage, then move to the numbers behind it.
The metrics row carries four figures: monthly total, annualised total, per-title annual, and borrow share. Monthly total is the number to trust most, because it involves the least extrapolation. Per-title annual is the number to compare across runs — it tells you whether a catalogue change raised or lowered each book's pace. Borrow share is context for the mix, not income itself.
The breakdown rows show where the monthly total comes from: ebook sales, borrows, and print, each with the units-times-royalty arithmetic written out. When one row dominates, your planning should focus there. A breakdown that reads 80 percent ebook sales points at price and conversion work; one that reads 50 percent borrows points at release cadence and series completion; one with meaningful print points at distribution and event stock.
The comparison table lists each title's annual pace beside its 20 percent illustrative lift. With large catalogues the table caps at ten rows so the page stays readable — multiply the per-title figures by your full count when you hold more than ten. Every figure in that table inherits the same straight-line assumption as the headline, so read across for scale and never down as a schedule of payments.
Why annualisation is not a forecast
Twelve multiplications hide at least five moving parts. Backlist sales decay after launch as visibility fades, usually settling to a fraction of release-month pace within a quarter. Promotions spike single months far above the baseline, and free or discount days can multiply volume tenfold for a week. New releases lift older titles through discovery while starting slow themselves. Seasons shift reading: holidays favour print and gifting, summer favours series bingeing, and January brings resolution-driven nonfiction. Prices, royalties, and borrow payments all change when platforms adjust terms.
None of those dynamics fit inside monthly-times-12, which is exactly why the tool labels its projection as arithmetic annualisation. The honest workflow is to re-run the estimate monthly with fresh inputs and watch the annualised figure drift. A catalogue whose annualised figure climbs three months in a row is growing; one whose figure falls while volume looks flat has a royalty or mix problem worth investigating. The trend across runs is the forecast-like signal, not any single run.
Taxes, fees, and advertising sit outside the tool on purpose. Royalties entered here are pre-tax receipts, ad spend is never subtracted, and subscription or service fees never appear. If you spend $300 a month on advertising against $876 of royalties, your kept income is the difference, and no output row will compute that for you. Keep a separate ledger for costs and compare its monthly total against this tool's monthly total.
Tracking these numbers month to month
A single estimate answers what the pace is today. Twelve estimates, one per month, answer where the catalogue is heading. Save each run's inputs and monthly total somewhere you will actually revisit — a spreadsheet row per month with titles, volume, royalties, borrow share, and the resulting monthly total takes two minutes to maintain and compounds into the most useful dataset an independent author can own. When the monthly total jumps, the saved inputs say why: volume rose, a royalty changed, or the mix shifted toward borrows.
For ongoing tracking, Author Desk at /author-desk is the natural home for this routine. Keep your title list and monthly volume figures there so each new estimate starts from last month's real numbers instead of memory, and review the annualised pace beside actual payouts as statements arrive. The habit matters more than the tool: a fresh run every month with honest inputs will teach you more about your catalogue's direction than any single projection, however carefully built.
Questions authors ask next
How often should the estimate be refreshed? Monthly, on the same day your statements close, so each run reflects a complete recent month. Quarterly at the absolute minimum — anything older than a quarter describes a catalogue that no longer exists.
Should box sets and bundles go in the same run as individual titles? Only when they share the same per-title pace, which they rarely do. A bundle moving 60 copies at a $5 royalty behaves like a premium title, not like an average of its contents. Give bundles their own run with their own figures.
What about audiobooks? Track them separately. Per-unit audio royalties, monthly units, and exclusive-versus-wide terms follow patterns this tool's three rows cannot represent, and folding audio dollars into ebook copies corrupts both. Add audio's monthly royalty total to this tool's monthly total yourself when you want the full picture.
Does going wide or exclusive change which fields matter? Exclusivity raises the borrow share field's importance because borrows become a large slice of income; wide distribution zeroes that field and puts all the weight on the ebook royalty. Authors considering a switch should run both versions — same volume at 60 percent borrows versus same volume at zero — and compare the monthly totals before deciding.
How dolaunch months fit in? They don't. Launch months combine pre-orders, rank boosts, and promotion stacking into volume no ordinary month will repeat. Annualising a launch month overstates the year badly. File launch months separately and annualise only ordinary months.
Can this replace accounting software? No. This tool sketches income pace from six inputs in seconds; accounting tracks received payments, withholding, fees, and costs across the year. Use the estimate for decisions and the accounts for truth, and reconcile the two whenever statements arrive.
Putting the estimate to work
Start with honest inputs from one ordinary month. Read the monthly total first and the annualised figure second, with the annualisation label firmly in mind. Check the breakdown for which platform carries the catalogue, and use the growth column to size one improvement — a price test, a promotion, a new release — rather than to promise yourself income. Then change one thing, wait a month, and run the numbers again. Authors who repeat that loop build catalogues whose pace rises on its own evidence, one measured month at a time.