DPI and PPI are two terms that often appear side by side in photo editors, printer dialogs, and internet debates — but while they sound similar, they describe different stages of the image process.
The good news? Once you know the difference, it’s easy to understand when each term matters — and when it doesn’t.
PPI: Pixels Per Inch
PPI refers to how many pixels fit into a single inch of space on a digital screen or layout. It’s a way of describing image resolution in terms of digital clarity.
- A 100 PPI image has 100 horizontal pixels per inch
- A 300 PPI image has 3× the pixel density — and appears sharper when printed
You’ll find PPI settings in image files themselves, and in layout software like Photoshop, Lightroom, or InDesign.
DPI: Dots Per Inch
DPI refers to how many printer dots are used per inch of paper when reproducing an image. It's about physical output — how an image is rendered in ink.
- A printer might interpret a 300 PPI image and output it at 600 or 1200 DPI depending on hardware
- DPI controls the density of ink dots, not the pixel count of the image
So What’s the Actual Difference?
| Feature | PPI | DPI |
|---|---|---|
| Stands for | Pixels Per Inch | Dots Per Inch |
| Used in | Digital images | Printers and ink output |
| Controls | Pixel density (resolution) | Print density (dot spacing) |
| Editable in | Image editors | Printer settings / drivers |
| Affects print size | Yes | Indirectly |
| Affects file size | No | No |
In practice, many tools (and people) use the terms interchangeably — especially since both relate to how large and how sharp an image will print.
When Should You Use PPI?
- When editing an image or exporting it for print
- When preparing a layout (like a photo book or poster)
- When converting image size into physical dimensions
Most photographers should think in PPI, because that’s what controls the effective print size for a given pixel resolution.
When Should You Care About DPI?
- When setting up your printer driver or print lab order
- When checking a printer’s spec sheet (e.g., “Prints at 1200 DPI”)
- If working in prepress or professional publishing
DPI is mostly a hardware setting — and not something you need to change inside your image files.
Summary
Think of it this way:
- PPI is for screens and image editing — how dense your image data is.
- DPI is for printers — how dense the dots of ink will be.
If you're preparing images for print, it’s helpful to know both. But in most cases, you’ll be setting PPI in your image, and your printer will handle DPI automatically based on its capabilities.