Amazon KDP is one of the more transparent royalty platforms — the rate is published, the maths is simple, the rules are well-documented. But the rules have non-obvious gotchas: the 70% royalty isn’t universal, the file-size delivery fee surprises new authors, and paperback is a completely different model.
The calculator above handles all three: ebook 70% vs 35% maths, the £1.99-£9.99 sweet spot, paperback print-cost calculations.
The 70% / 35% decision
For ebooks, you choose either 70% or 35% royalty when you publish. The choice isn’t free — 70% has restrictions:
- List price £1.99-£9.99 in the UK store (the US store has an equivalent range in dollars). Outside this range, you’re forced to 35%.
- Delivery fee charged at ~£0.10 per MB. Most plain-text books are 1MB; image-heavy books can be 10MB+. The fee comes off your 70% royalty.
- Distribution restrictions in some markets (mainly outside US/UK/EU; Brazil/Mexico/India default to 35% unless you’re in KDP Select).
The numbers, for a 1MB ebook at typical prices:
| List price | 35% royalty | 70% royalty | Better |
|---|---|---|---|
| £0.99 | £0.35 | not eligible | 35% (forced) |
| £2.99 | £1.05 | £2.02 | 70% |
| £4.99 | £1.75 | £3.42 | 70% |
| £7.99 | £2.80 | £5.52 | 70% |
| £9.99 | £3.50 | £6.92 | 70% |
| £12.99 | £4.55 | not eligible | 35% (forced) |
The 70% rate is roughly 2x the 35% rate at the same price point. Pricing strategically inside the £1.99-£9.99 range is one of the biggest decisions a KDP author makes.
File size matters more than authors realise
The £0.10/MB delivery fee on 70% mode quietly punishes image-heavy books:
- 1MB book: £0.10 delivery fee, £3.42 royalty on £4.99 list (70%)
- 5MB book: £0.50 delivery fee, £3.14 royalty on £4.99 list (70%)
- 10MB book: £1.00 delivery fee, £2.79 royalty on £4.99 list (70%)
Cookbooks, photography books, illustrated children’s books, and design references can easily be 10-30MB if not optimised. Compress images, use efficient formats, and the savings are direct margin. A photography book optimised from 25MB to 5MB saves £2.00 of delivery fee per copy — at 1,000 copies that’s £2,000.
Paperback: a different game
Paperback uses a completely different model:
Royalty = list price - print cost - (list × 40% Amazon take)
Print cost = £0.85 + £0.012 × page count (B/W; colour is more)
So a 200-page paperback at £9.99: - List: £9.99 - Print: £0.85 + £2.40 = £3.25 - Amazon take: £9.99 × 40% = £4.00 - Royalty: £9.99 - £3.25 - £4.00 = £2.74
The 40% Amazon cut + variable print cost means paperback economics are completely different from ebook. Three rules of thumb:
- Page count matters a lot. A 400-page paperback costs £5.65 to print — the breakeven is much higher.
- Lower-page books work at lower prices. A 100-page paperback at £6.99 royalties £2.34 (workable). A 100-page paperback at £9.99 royalties £3.94 (good).
- Don’t price paperback identical to ebook. Most successful KDP authors set paperback ~50-80% above ebook price.
KDP Select trade-off
KDP Select is Amazon’s exclusivity programme. Enrol your ebook for 90 days, can’t sell it on other ebook platforms, in exchange for:
- Kindle Unlimited inclusion — KU subscribers can borrow your book; you earn ~£0.005 per page read. For genre fiction with engaged readers, KU income often exceeds direct sales.
- 70% royalty in additional markets — Brazil, Mexico, India, Japan default to 35% outside Select; in Select they get 70%.
- Promotional tools — Free Days, Countdown Deals (time-limited price drops with maintained 70% royalty).
The cost is exclusivity. Apple Books, Kobo, Google Play, Barnes & Noble — all locked out. For some authors this loses 30-50% of revenue (audience reads on those platforms); for others it gains 30-50% from KU pages-read.
Genre fiction writers with active KU-reading audiences often win with Select. Niche non-fiction authors with reader bases on Apple Books or Kobo often lose. Run the maths after first publishing wide for 6 months, then making the call.
What this calculator doesn’t model
- KDP Select / Kindle Unlimited pages-read income — separate revenue stream not modelled
- Marketing costs — Amazon Ads, BookBub features, blog tour costs typically £200-£2,000 per launch
- Series economics — book 1 free / £0.99 + book 2-7 full price model
- US/EU market pricing — UK only here
- Income tax — see side hustle tax calculator
Tax: it’s all self-employment income
KDP royalties are UK self-employment income. Above £1,000 trading allowance: income tax + Class 4 NI on net (royalties minus expenses like editing, cover design, marketing). Amazon withholds US tax automatically (after you file W-8BEN); UK tax is your responsibility via Self Assessment.
Many authors treat KDP as their primary income — for them, the earn-to-quit-job calculator shows the gross royalty volume needed to replace a day job. For most authors KDP is a side income; the side hustle tax calculator handles stacking on top of PAYE.