DPI vs PPI Explained: What You Need to Know for Printing and Screens
DPI and PPI are often confused but mean different things. This plain-English guide explains both, when each matters, and how to set the right value for your images.
DPI and PPI appear on every print dialog and image editing app, yet most people use them interchangeably. They are related but distinct concepts — and confusing them can lead to blurry prints or unnecessarily huge files.
PPI: Pixels Per Inch (Screen Resolution)
PPI describes the density of pixels on a screen. A standard HD monitor displays at ~96 PPI. A Retina MacBook Pro displays at 220 PPI. iPhones display at 460 PPI. Higher PPI means sharper, crisper images. PPI is a property of the display device, not the image file. When someone says 'this image is 72 PPI', they mean the embedded metadata says 72 — this has no effect on how the image looks on screen or on its file size. What matters for screen display is the raw pixel count.
DPI: Dots Per Inch (Print Resolution)
DPI describes the density of ink dots a printer places on paper. Most photo printers operate at 300–600 DPI. Magazine printing uses 300 DPI. Large-format poster printing can use 150 DPI (viewed at distance). For a print to look sharp, you need enough pixels in your image to fill the physical dimensions at the required DPI. This is calculated as: Required pixels = print size in inches × DPI
Required Pixel Counts for Common Print Sizes at 300 DPI
| Print Size | Pixels Required |
|---|---|
| 4×6 inch | 1200×1800px |
| 5×7 inch | 1500×2100px |
| 8×10 inch | 2400×3000px |
| A4 (8.27×11.69 inch) | 2480×3508px |
| A3 (11.69×16.54 inch) | 3508×4961px |
| Passport 35×45mm | 413×531px |
Does the Metadata DPI Setting Actually Matter?
The DPI value embedded in an image file (in EXIF or JFIF data) tells printers and layout software how to interpret the image. If you have a 1200×1800px image with embedded DPI of 300, software correctly reads it as 4×6 inches at print quality. If the embedded DPI is 72, the same image would be interpreted as 16.7×25 inches — too large for a standard print. Changing the embedded DPI value does not change the pixel count. It only changes how software sizes the image by default. You can set it freely without affecting image quality.
Setting DPI in ImageResize.co
Our Image Resizer and passport photo tools (35×45mm, 2×2 inch) automatically set the correct pixel dimensions and embedded DPI for their specific use cases. For custom print sizes, enter your target pixels manually.
Quick Reference
- Web images: DPI metadata is irrelevant. Only pixel dimensions matter.
- Print images: You need pixels = inches × DPI. Use 300 DPI for photo-quality prints.
- Passport photos: Government requirements are in millimetres — the 35×45mm tool handles the conversion automatically.
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