Pixels are what count
A digital photo is a grid of pixels, for example 4000 × 3000. DPI (dots per inch) or PPI only says how densely those pixels should be printed. The same 4000 × 3000 photo printed at 300 dpi is 13.3 × 10 in (34 × 25 cm); at 150 dpi it is twice as big but less sharp.
The formula
Print size (inches) = pixels ÷ dpi, and pixels needed = inches × dpi (1 inch = 2.54 cm).
| Use | Recommended dpi |
|---|---|
| Photo prints viewed up close | 300 dpi |
| Posters viewed from a distance | 150–200 dpi |
| Large banners | 50–100 dpi |
| Screens and websites | DPI is ignored — only pixel dimensions matter |
The “72 dpi for web” myth
Browsers and phones display images by pixel size and ignore the dpi value stored in the file. A 1200 px wide image looks the same whether its metadata says 72 or 300 dpi. To make web images smaller, reduce pixel dimensions with Resize image and compress them — changing dpi alone does nothing.
Will my photo print sharply?
- Check the pixel size (the tools on this site show it on every image).
- Divide by 300 to get the sharp print size in inches (multiply by 2.54 for cm).
- If it is too small, choose a smaller print instead of enlarging — upscaling does not add real detail.
Frequently asked questions
The print shop says my photo is 72 dpi — is it bad?
Not necessarily. If it has enough pixels for the print size, it will print well. Some shops simply read the metadata value; the pixel count is what matters.