# DPI (dots per inch)

> Source: https://www.infinitelibrary.ai/glossary/dpi

Last updated: 2026-09-06
Category: Printing & binding
Also called: PPI (pixels per inch) · Image resolution

DPI is print resolution in dots per inch; book images need 300 pixels per inch at their printed size, so a 6-inch-wide photo needs 1,800 pixels across.

## Definition

**DPI** (dots per inch) describes how finely a printer lays ink; **PPI** (pixels per inch) describes how much image data exists for each printed inch. The two are used interchangeably, and what a book printer cares about is the second: an image should supply **300 pixels for every inch it will be printed**. Below about 200 ppi photographs soften; below 150 they look pixelated. Line art and text as images need more — 600 to 1,200 ppi — because hard edges show every step.

The arithmetic is simple. A photo printed 6 in wide at 300 ppi needs at least 1,800 pixels across; a full-bleed 8.5 × 8.5 in picture-book page needs about 2,600 × 2,600. Resolution is a ratio, not a property of the file: the same 1,800-pixel image is 300 ppi at 6 in and only 150 ppi at 12 in.

Upscaling in software invents pixels; it cannot add detail. Start from the largest original you have.

## Related

- [CMYK vs RGB](https://www.infinitelibrary.ai/glossary/cmyk-vs-rgb)
- [Print-ready PDF (PDF/X)](https://www.infinitelibrary.ai/glossary/print-ready-pdf)
- [Preflight](https://www.infinitelibrary.ai/glossary/preflight)
- [Bleed](https://www.infinitelibrary.ai/glossary/bleed)
- [Photo Book Maker](https://www.infinitelibrary.ai/formats/photo-book-maker)
- [Travel Photo Book Maker](https://www.infinitelibrary.ai/formats/travel-photo-book-maker)
- [Children's Picture Book Maker](https://www.infinitelibrary.ai/formats/childrens-picture-book-maker)
- [Book Publishing Glossary — 59 Terms Defined](https://www.infinitelibrary.ai/glossary)
- [Bindery — the Claude-powered book studio](https://www.infinitelibrary.ai/bindery)

---

More from Infinite Library, as one map for AI agents: https://www.infinitelibrary.ai/llms.txt