Practical guide 3 min read
What DPI means, and how to get a 300 DPI image
Why DPI changes print size and not quality, how large your photo can print, and how to set 300 DPI without re-compressing it.
DPI is a print instruction, not image quality
A digital image is a grid of pixels, such as 3000 × 2000. DPI (dots per inch) is a separate number stored in the file. It tells printing software how many of those pixels to fit into each inch of paper.
That is why changing the DPI doesn't make an image sharper or blurrier. The pixels stay exactly the same, and only the printed size changes. Strictly, the setting is PPI (pixels per inch), but almost everyone, including most printers and forms, calls it DPI.
Work out how big a photo can print
Divide the pixel dimensions by the DPI:
print size in inches = pixels ÷ DPI
A 3000 × 2000 pixel photo at 300 DPI prints at 10 × 6.7 inches. At 150 DPI, the same photo prints at 20 × 13.3 inches, with each pixel twice as big on paper.
300 DPI is the usual standard for photos and documents viewed up close. These are the pixel dimensions you need for common print sizes at 300 DPI:
| Print size | Pixels needed at 300 DPI |
|---|---|
| 4 × 6 in | 1200 × 1800 |
| 5 × 7 in | 1500 × 2100 |
| 8 × 10 in | 2400 × 3000 |
| A4 (8.3 × 11.7 in) | 2480 × 3508 |
| US Letter (8.5 × 11 in) | 2550 × 3300 |
Most modern phone photos have more than enough pixels for an 8 × 10 print.
Set an image to 300 DPI, step by step
Change Image DPI is free and needs no account.
- Open Change Image DPI and choose or drop your JPG or PNG images.
- Pick the DPI you need: 72, 96, 150, 300, 600 or Other. The print size that gives appears as you choose, in inches and centimetres.
- Select Change DPI and download the images.
The images come back pixel-for-pixel unchanged, and JPGs are not re-compressed. Only the DPI setting in the file is rewritten.
When the printer says the image is too small
If a print shop or publisher says your image is not 300 DPI at the size they need, the problem is pixels, not the setting. Changing the DPI to 300 just makes the image print smaller.
Your options:
- Print it smaller. Use the formula above to find the largest size your pixels allow at 300 DPI.
- Accept a lower DPI. For posters and banners seen from a few steps away, 150 DPI usually looks fine.
- Find a larger original. Photos sent through messaging apps or downloaded from social networks are often shrunk. The original on the phone or camera may have far more pixels.
Enlarging the image with Resize Image adds pixels, and some printers accept that, but it cannot add real detail. Enlarged images look soft up close.
When a form asks for pixels and DPI
Some applications ask for both, for example "600 × 600 pixels at 300 DPI". That describes a 2 × 2 inch photo. Resize to the pixel dimensions first with Resize Image, then set the DPI on the resized copy.
If the form also has a file size limit, compress the image last and check that the dimensions are still right. The guide to compressing an image below 100 KB covers that step.
Which formats store a DPI?
JPG and PNG both store a DPI, and both are changed without re-compressing. WebP and HEIC have no DPI setting, so the tool converts them to JPG or PNG first and tells you it has done so.
On screens, DPI makes no difference at all. A web page or slide shows the pixels at whatever size the layout gives them, so 72 and 300 DPI images look identical on screen.
Where your images are processed
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