Change Image DPI

Change Image DPI rewrites the small “dots per inch” note stored inside a JPG or PNG file. Printers, design apps and many online forms read that note to decide how big the picture should come out on paper, which is why a shop or an application portal may insist on “300 DPI”. The picture itself does not change at all: we edit only the file header and copy the image data across byte for byte, so there is no re-compression and no quality loss.

It suits anyone who has been told a file “must be 300 DPI”: people sending photos to a print lab, students submitting a poster, designers preparing artwork for a magazine, or someone uploading a passport-style photo to a government site. You see the DPI each file has now, its size in pixels, and how big it will print at the DPI you choose, in centimetres and inches.

Everything runs in your browser. Your photos are not uploaded, there is no sign-up, and after saving each file the tool reads it back to confirm the new DPI is there and the picture data is unchanged.

1. Tap “Choose files”, drop images on the box, or paste one. Each row shows its pixel size and current DPI.
2. Pick a DPI: 72, 96, 150, 300, 600, or “Custom” to type any value. The print size panel updates as you choose.
3. For files that aren’t JPG or PNG, choose whether they should be saved as PNG or JPG.
4. Press “Set 300 DPI” (the button names your choice). Each row shows the new DPI and print size when it is done.
5. Press “Download” to save one image, or the whole batch as a ZIP. Use the reverse calculator below to work out the pixels a print needs.

• JPG: updates the JFIF header (and adds one if the file has none), and keeps the EXIF resolution tags in step where they exist.
• PNG: writes a fresh pHYs block (the PNG’s own DPI record) with a correct checksum, replacing any old one.
• No re-encoding for JPG and PNG: the compressed picture data is copied byte for byte, so colours, sharpness and CMYK files stay untouched.
• WebP, HEIC, AVIF, GIF, BMP, TIFF and SVG are converted to PNG or JPG first, since those formats have no dependable DPI setting.
• Shows the current DPI read from each file, its pixel size, and the print size in centimetres and inches at your chosen DPI.
• Presets for 72, 96, 150, 300 and 600 DPI, plus any custom value from 1 to 65,535.
• Reverse calculator with common print sizes: 10 × 15 cm at 300 DPI needs 1181 × 1772 px, and it tells you what DPI your own photo would reach.
• Batch up to 100 images and download them together as one ZIP.
• Every saved file is read back and checked before you can download it.

• DPI alone does not add detail. If the print size panel shows a small size at 300 DPI, the photo simply has too few pixels for a bigger sharp print; use the reverse calculator to see what you would need.
• If a print shop wants a set size, crop the photo to that shape first, then set the DPI here.
• Some forms check pixel size, not DPI, even when they say “300 DPI”. If the upload is still refused, compare their pixel limits with the size shown in your row.
• For photo prints, 300 DPI is the usual target; 150 is fine for posters seen from a distance, and 600 suits line art and scans of text.