Guide 02

Understanding BISAC codes and choosing yours

BISAC codes are the filing system retailers use to shelve your book. Pick wrong and Amazon puts you in the wrong category; pick right and your book shows up alongside the ones readers are already buying.

Last updated Apr 21, 2026v1 · pending Spellbound

BISAC — Book Industry Standards and Communications — is the categorisation system every major retailer uses to decide where your book lives. Amazon asks for two to three BISAC codes when you publish. Those codes feed directly into what "Categories" your book appears under, which feeds into your Best Seller Rank (BSR) and, indirectly, what readers see in "Customers Also Bought".

Pick the wrong BISAC and you're competing with the wrong books. Pick the right one and your book shows up in lists readers are already scrolling.

The shape of a code

Every BISAC code is three uppercase letters plus six digits — nine characters total. Examples:

FIC009020 → FICTION / Fantasy / Epic
FIC028070 → FICTION / Science Fiction / Hard Science Fiction
FIC027050 → FICTION / Romance / Historical / General

The letters are the top-level category (FIC = fiction, BIO = biography, BUS = business). The digits narrow it down. Our BISAC picker on /new has a curated starter set of around 50 codes covering the genres indie novelists actually publish in. For codes outside our list, type the nine-character format and the picker lets you add it with a "verify at bisg.org" warning.

The hard part: picking the right ones

Amazon lets you pick up to three. You should pick three, not one. Here's how to think about it:

Code one — the spine. The single most accurate category for the book. This is the one you'd answer with if someone said "what genre is this?" in a single sentence. For Spellbound, a first-contact sci-fi novel set in a dystopian arcology, that's probably FIC028100 (Apocalyptic & Post-Apocalyptic) — with the caveat that "apocalyptic" in BISAC covers both post-apocalyptic and approaching-apocalyptic works.
Code two — the audience expander. A nearby-but-not-identical category where your book also legitimately belongs. For Spellbound, FIC055000 (Dystopian) covers a different reader set with overlap.
Code three — the lane you want to be in. A slightly narrower category where your book can actually rank because fewer books compete there. Avoid the /General leaf nodes (e.g. FIC028000 FICTION / Science Fiction / General) — they're crowded with every sci-fi book ever, and you won't rank.

Things not to do

Don't pick three near-identical codes. If all three resolve to slightly-different flavours of the same subgenre, you're wasting slots.
Don't pick a category you're not actually in just because it ranks well. Amazon reviewers notice and the categories get pulled; worse, readers who bought expecting one thing leave angry reviews.
Don't pick /General for your spine. It's always the most crowded leaf. If your book is fantasy, pick the flavour of fantasy (epic, urban, paranormal, dark), not just "fantasy".
Don't duplicate what's in your title or subtitle. If "A Dystopian Novel" is your subtitle, the Dystopian BISAC is already implied; spend the slot on something else.

What happens after you submit

Amazon uses your three BISAC codes to map into their own category tree, which is bigger and more granular than BISG's. A single BISAC might map into one, two, or three Amazon categories depending on the country marketplace. You can later email KDP support and ask for additional categories (up to ten total across Amazon's tree) if you have specific ones in mind — but start with three solid BISACs and let the machine do its job first.

The short version

Open /new, fill in the book up to Book details, and use the BISAC picker.
Pick one spine code that describes the book accurately.
Pick one expansion code (related subgenre with partial overlap).
Pick one narrow lane where fewer books compete — not a /General.
Generate. Amazon will map these into its category tree at upload.

Anthony's take