DPI vs Pixels: Image Resolution Explained Clearly
Understand pixels, DPI and PPI, why changing DPI may not change an image on screen, and how to calculate print size.
Pixels describe the image
A 3000 × 2000 image contains six million pixel positions whether its resolution field says 72, 96 or 300. Browsers normally size raster images with CSS and pixel dimensions, not print-density metadata.
Print size is a calculation
At 300 pixels per inch, a 3000-pixel image prints about 10 inches wide. At 150, it covers about 20 inches but may look less sharp close up.
Formula: print inches = pixel dimension ÷ target pixels per inch.
Why changing DPI may do nothing
If an editor changes only metadata without resampling, pixel count and screen appearance stay unchanged; only suggested physical size changes. With resampling, software creates or removes pixels.
Choose by destination
- Website: use rendered pixels and responsive sources.
- Office print: confirm printer needs and viewing distance.
- Professional print: ask for dimensions, bleed, colour and resolution requirements.
Practical steps
- Read the actual pixel dimensions.
- Ask for the intended screen or physical size.
- Calculate print size from pixels per inch when printing.
- Resample only when the required pixel count changes.
Common mistakes
- Treating 72 DPI as a web requirement.
- Changing a DPI field and expecting more captured detail.
- Ignoring viewing distance and printer requirements.
Frequently asked questions
Is 72 DPI required for web?
No. Pixel dimensions and file weight normally matter to browser display.
Does 300 DPI improve a small image?
Not alone. Without resampling it changes metadata; with it, pixels are invented.