DPI and PPI Explained: Resolution for Print and Screen
"What DPI should I save my image at?" is a question that confuses even experienced designers. The answer depends entirely on whether your image is destined for screen or for print.
Definitions
PPI — Pixels Per Inch (screens)
PPI describes the density of physical pixels on a display. It's a hardware characteristic:
- 24" Full HD monitor ≈ 92 PPI
- 14" Retina MacBook Pro ≈ 254 PPI
- iPhone 15 ≈ 460 PPI
When designing for the web you don't control the PPI of your users' devices. What you control is the total pixel dimensions of your image.
DPI — Dots Per Inch (printing)
DPI describes how many ink dots a printer lays down per linear inch. Technically it's a printer characteristic, but in practice it's used to indicate the resolution of an image intended for print.
Although DPI and PPI describe different things, in graphic design they're used interchangeably when talking about image resolution. In this context, DPI = image PPI.
Standard resolutions for printing
| Use case | Minimum DPI | Recommended DPI |
|---|---|---|
| Letters / documents | 150 | 300 |
| High-quality photo printing | 240 | 300 |
| Offset printing (magazines, books) | 300 | 300–350 |
| Large format (posters > A1) | 72–100 | 150 |
| Billboards | 10–30 | 72 |
| Screen / web | 72 (irrelevant) | 72–96 |
The logic: the larger the physical medium, the lower the DPI you need because viewers stand farther away.
For screens, DPI doesn't matter
When exporting for web or social media, the DPI metadata is irrelevant. Browsers and apps only read total pixel dimensions. A 1920×1080 PNG at 72 DPI and the same PNG at 300 DPI are exactly the same file visually — the only difference is a metadata value in the file header.
What actually matters for screen:
- Total pixels (width × height)
- File weight (optimization for fast loading)
How to calculate print size
Formula: Physical size = Pixels ÷ DPI
Example: 3000×2000 px image at 300 DPI:
- Width: 3000 ÷ 300 = 10 inches (25.4 cm)
- Height: 2000 ÷ 300 = 6.67 inches (16.9 cm)
To print at A4 (8.27×11.69 inches) at 300 DPI you need:
- 8.27 × 300 = 2,481 px minimum width
- 11.69 × 300 = 3,508 px minimum height
How to change image DPI
Change metadata only (no pixel change)
This does not change the pixel count. It only adjusts the metadata telling the printer how to scale the image:
- Photoshop: Image → Image Size → uncheck "Resample" → change Resolution
- GIMP: Image → Scale Image → change only DPI, leave pixel dimensions untouched
Resample (changes actual pixels)
If your image has too few pixels for the desired print size, you need to upsample. Result quality depends on the algorithm:
- Bicubic: smooth result, slight softening
- Lanczos: better for text and illustrations
- AI-based (Topaz Gigapixel, Adobe Enhance): best for real photographs
Remember: adding pixels artificially never recovers detail that didn't exist in the original.
Quick reference
| Destination | What you need |
|---|---|
| Web / social media | Correct total pixels (e.g., 1200×630 for OG), DPI irrelevant |
| 4×6" photo print | At least 1200×1800 px at 300 DPI |
| A4 brochure | At least 2481×3508 px at 300 DPI |
| A0 poster (33×47") | ~9933×14043 px at 300 DPI, or ~4961×7021 px at 150 DPI |
| 10×20 ft billboard | 1000×500 px can suffice at 10 DPI |
Understanding the relationship between pixels, DPI, and physical size lets you prepare images perfectly for every destination — without surprises in the final output.
Related conversions
Frequent conversions across the catalogue: