A photo that looks crisp on your phone can come out of the printer soft and pixelated. The cause is almost always the same: the image doesn't have enough pixels for the size you chose. Once you understand how pixels, DPI and print size relate, you can check any photo in seconds before you print it.
Pixels, DPI and print size
A digital image is a grid of pixels. A print has a physical size in inches or centimetres. DPI (dots per inch, often written PPI for pixels per inch) describes how many pixels are packed into each inch of the print.
The relationship is simple:
pixels needed = print size in inches × DPI
A 6-inch-wide print at 300 DPI needs 6 × 300 = 1800 pixels across. If your image has fewer pixels than that, the printer has to stretch them, and the result looks soft.
The DPI number in the file doesn't change quality
This is the most common misunderstanding. An image file can carry a "DPI" tag such as 72 or 300, but that tag is just a suggestion for default print size. It does not add or remove detail. A 1200 × 1800 pixel image is exactly the same picture whether it's labeled 72 DPI or 300 DPI. What matters is the actual pixel count compared with the print size.
So "converting 72 DPI to 300 DPI" without changing the pixel dimensions doesn't make an image sharper. To get a sharp print, you need enough real pixels.
Which DPI should you aim for?
- 300 DPI is the usual target for photos and anything viewed up close. At this density, individual pixels are invisible.
- 150 to 200 DPI can still look good for larger prints viewed from a bit further away, such as posters and wall art.
- Very large formats like banners are viewed from a distance, so much lower DPI is often acceptable.
When in doubt, check what your print service recommends, as their requirements can differ.
Pixel sizes for common print sizes at 300 DPI
| Print size | Pixels needed |
|---|---|
| 4 × 6 in (10 × 15 cm) | 1200 × 1800 |
| 5 × 7 in | 1500 × 2100 |
| 8 × 10 in | 2400 × 3000 |
| A4 (8.27 × 11.69 in) | about 2480 × 3508 |
| 11 × 14 in | 3300 × 4200 |
A modern phone photo of 12 megapixels is roughly 4000 × 3000 pixels. That comfortably covers 8 × 10 at 300 DPI and even larger prints at somewhat lower density.
How to resize an image for print
If your image is much larger than you need, resizing it down is safe and can make uploads to a print service faster. If it is smaller than you need, read the next section first.
- Work out the pixels you need using the formula above.
- Open the image resizer.
- Enter the target width and height, or pick the closest preset.
- Choose how the image should fit the shape: Crop fills the whole canvas by trimming the edges, Fit keeps everything and adds bars. Different aspect ratios matter here, since a 4:3 phone photo doesn't match a 4 × 6 print, which is 3:2.
- Download the result.
If you only want to make sure a huge photo is never enlarged, the Inside option shrinks oversized images and leaves smaller ones alone.
What if your photo has too few pixels?
Enlarging a small image just spreads the same information over more pixels, which looks soft. You have two honest options: print smaller, or use an AI upscaler that predicts added detail. Our AI image upscaler can help, and our article on how AI upscaling really works explains what it can and cannot do.
Quick checklist
- Multiply print size in inches by 300 to get the pixels you need.
- Ignore the DPI label in the file; count real pixels.
- Match the aspect ratio of the print, or crop to it.
- Keep your original and resize a copy.