How to use it
- Type the DPI you need. 300 is the usual requirement for print.
- Add your images. Each shows the size it will print at.
- Download.
What DPI actually is in a file
An image file is a grid of pixels. The DPI value stored with it is just a note saying how many of those pixels should be printed per inch. Change the note from 72 to 300 and the pixels stay exactly the same; the only thing that changes is the default print size. A 3000 × 2000 pixel photo is 10 × 6.7 inches at 300 DPI, or 41.7 × 27.8 inches at 72 DPI, and it is the same file either way.
That is why this tool can change the DPI losslessly. For JPGs it updates the JFIF header and the EXIF resolution fields; for PNGs it writes a pHYs chunk. Nothing else is touched.
When a printer asks for 300 DPI
Print shops and publishers ask for 300 DPI because at normal reading distance, that is about as fine as the eye can resolve. What really matters is whether you have enough pixels for the print size. Multiply the print size in inches by 300 to see what you need: a 6 × 4 inch print wants 1800 × 1200 pixels. If your image has that many or more, setting 300 DPI here will satisfy a form or a picky piece of software. If it has far fewer, changing the label will not add detail. StatGarden's print resolution calculator works out either side of that sum.
For a longer explanation, see DPI is mostly a label.
Questions people ask
Does changing DPI change image quality?
No. The pixels are identical; only the print-size tag changes.
How do I make an image 300 DPI?
Enter 300 and add the image. The downloaded file is tagged 300 DPI with every pixel unchanged.
Why does my image still look blurry when printed at 300 DPI?
It does not have enough pixels for the print size. You need about 300 pixels per inch of print, per side.
Does DPI matter for websites?
No. Browsers ignore the DPI tag and use pixel dimensions only.