Images
What is DPI?
Short for Dots per inch. Also called PPI or print resolution.
DPI, or dots per inch, is a print setting that says how many image pixels should fill each inch of paper. It doesn’t change the pixels themselves.
How it works
An image file is a grid of pixels with no physical size. DPI is a number stored alongside that grid which tells a printer how densely to lay the pixels on paper. Higher DPI packs them closer together, making a smaller, sharper print; lower DPI spreads them out.
The only quantity that sets how much detail an image holds is its pixel count. Two copies of the same photo tagged 72 DPI and 300 DPI contain identical pixels and look identical on screen. They would only differ when printed without scaling.
DPI vs pixel dimensions
| Print size | Pixels needed at 300 DPI | At 150 DPI |
|---|---|---|
| Passport photo (2 × 2 in) | 600 × 600 | 300 × 300 |
| 4 × 6 in | 1200 × 1800 | 600 × 900 |
| A4 / Letter page | about 2500 × 3300 | about 1250 × 1650 |
300 DPI is the usual target for close viewing such as photos and brochures. Posters seen from a distance look fine at 150 DPI or less.
A practical example
A 3000 × 2000 pixel photo printed at 300 DPI comes out 10 × 6.7 inches. Set to 150 DPI, the same file prints at 20 × 13.3 inches with less sharpness.
What to watch out for
Changing the DPI number alone doesn’t add detail or change file size. A form that asks for a 300 DPI image usually wants enough pixels for a certain print size, so check the pixel dimensions.
Tools you can use
- Image Resizer · Scale to a size, a percentage or a platform preset
- Image to PDF · Turn photos and scans into one document
Go a little deeper
- How to make an image 300 DPI
- How to resize an image for a website
- How to make a PDF from photos on an iPhone
- Prepare documents for an online application
Common questions
How do I make an image 300 DPI?
Work out the print size you need and multiply by 300. A 4 × 6 inch print needs 1200 × 1800 pixels. If the image already has that many, only the DPI tag needs changing; if not, enlarging it won’t add real detail.
Does DPI matter for screens?
No. Screens show images pixel for pixel, so a 1000-pixel-wide image looks the same whether its DPI tag says 72 or 300.
What is the difference between DPI and PPI?
PPI (pixels per inch) describes an image or screen, while DPI strictly describes a printer’s ink dots. In everyday use, including upload forms, the two mean the same thing.