The mass market paperback is the small, cheap, pocket-sized paperback — the airport thriller, the supermarket romance, the rack of spinning novels by the till. It is a specific format with a specific size, and it is worth knowing the numbers, because most self-publishing routes cannot print one.
The dimensions
A US mass market paperback is about 4¼ inches wide by 6⅞ to 7 inches tall — roughly 108 by 175 to 178 mm. Publishers vary by a fraction of an inch; the width is the constant, because it is what fits the rack. The earliest mass-market paperbacks in the 1930s and 40s were a little shorter, and the format settled at around 7 inches tall by the 1950s.
The British equivalents:
| Format | Size | Used for |
|---|---|---|
| A-format | 110 × 178 mm (about 4⅜ × 7 in) | The UK mass market paperback |
| B-format | 129 × 198 mm (about 5⅛ × 7¾ in) | The standard UK paperback novel |
| C-format / trade | 135 × 216 mm (about 5⅜ × 8½ in) | Larger paperbacks, often the first paperback edition |
"Mass market" and "A-format" are the same idea on two sides of the Atlantic: the smallest trade size, printed on inexpensive paper, priced to move.
Mass market vs trade paperback
The other paperback is the trade paperback, which in the US is anything from about 5 × 8 inches up to 6 × 9, printed on better paper, sold in bookshops rather than racks, and priced accordingly. Most new novels appear first as a hardback, then as a trade paperback, and only reach mass market if they sell enough to justify a cheap edition.
The differences are more than size:
- Paper. Mass market books are printed on groundwood paper — the stock newspapers use — which is thin, off-white, and yellows. Trade paperbacks use a heavier, whiter stock.
- Type. To fit a full novel into a small page, mass market editions are set tight: small type, narrow margins, little leading. Trade paperbacks are set for comfort.
- Returns. Mass market paperbacks are traditionally strippable — a bookseller returns only the torn-off cover for credit and pulps the rest. This is why the inside of a mass market cover often carries a notice about books sold without a cover.
Can you self-publish at mass market size?
Not on Amazon KDP. KDP's smallest paperback trim is 5 × 8 inches; nothing on its list of sixteen trims is narrower than 5 inches, and the only ones under 7.81 inches tall are the landscape and square formats meant for picture books. There is no mass market or A-format option, and no way to add a custom size below the minimum.
On IngramSpark, in principle. IngramSpark accepts paperbacks from 4 × 6 inches up, on white paper, so a 4.25 × 7 book is inside the range. Whether it is a good idea is another matter: print-on-demand cannot use groundwood paper or the economies of a 100,000-copy print run, so a POD book at mass market size costs about what a trade paperback costs to make and sells for less. The format exists because of scale, and print-on-demand has none.
For a self-published novel the practical answer is a trade size. The nearest KDP trim to the feel of a mass market book is 5 × 8 or 5.06 × 7.81, which is B-format territory — a small, hand-sized paperback that still prints economically. Choosing a trim size compares the options, and book margins and gutters explains why a small trim with a long book runs into margin trouble.
Setting a small book
Whatever the trim, a small page has less room, and the temptation is to shrink the type. Resist it. A mass market book gets away with 9-point type on a tight measure because readers accept it as the price of the format; a self-published trade paperback at 5 × 8 is judged against other trade paperbacks, and 10½ to 11 point on a comfortable leading is where those sit. The page count goes up, the print cost goes up a little, and the book is readable. The print formatter sets any KDP trim with mirrored margins and a gutter sized to the page count, so the numbers work out before you order a proof.
The short version
- US mass market: about 4¼ × 7 inches (108 × 178 mm). UK A-format: 110 × 178 mm. UK B-format: 129 × 198 mm.
- It is a cheap-paper, high-volume format, not just a small one.
- KDP's smallest trim is 5 × 8. IngramSpark goes down to 4 × 6, but print-on-demand loses the economics that make the format work.
- For a self-published novel, 5 × 8 or 5.06 × 7.81 is the small-book choice.