DPI Changer
Set a JPG or PNG to 300 DPI without re-compressing it. Free, no upload.
Print size calculator
DPI does not add detail. It only tells printers and layout programs how many pixels to put in each inch. The pixels stay exactly as they were.
How It Works
Pick a JPG or PNG. The tool reads its pixel size and the DPI stored in its header, then shows how large it prints. Choose a new DPI and save. Only the resolution numbers in the header are rewritten; the image data is copied unchanged, so nothing is re-compressed.
- JPEG: sets the JFIF density (adding a JFIF header if the file has none), plus the EXIF XResolution, YResolution and ResolutionUnit tags and Photoshop's resolution record when they are present.
- PNG: writes a pHYs chunk in pixels per metre, replacing any existing one, with a correct checksum.
Read more in the guide: How to change an image to 300 DPI.
What DPI Actually Means
A digital image is a grid of pixels. It has no physical size until it is printed. DPI (dots per inch, also called PPI for images) is a single number in the file that says how many of those pixels should fit into one printed inch.
Print size = pixels ÷ DPI. A 3000 × 2000 pixel photo at 300 DPI prints at 10 × 6.67 inches. Set it to 72 DPI and the same file asks for 41.67 × 27.78 inches. Same pixels, same file, same sharpness on screen.
That is why a print shop asking for "300 DPI" really needs two things: enough pixels for the size you want, and the DPI field set so their software lays it out at that size. This tool fixes the second. If you are short on pixels, the table below shows how many you need.
Pixels Needed at 300 DPI
| Print size | Pixels at 300 DPI |
|---|---|
| 4 × 6 in | 1200 × 1800 |
| 5 × 7 in | 1500 × 2100 |
| 8 × 10 in | 2400 × 3000 |
| US Letter, 8.5 × 11 in | 2550 × 3300 |
| A4, 210 × 297 mm | 2480 × 3508 |
| A5, 148 × 210 mm | 1748 × 2480 |
Many photo labs accept less than 300 DPI for larger prints that are viewed from further away. Check what your printer recommends.
Frequently Asked Questions
Does changing the DPI make my image sharper or higher quality?
No. DPI is a number stored in the file that tells programs how large to print it. The pixels stay exactly the same, so the image has the same detail at 72 DPI as at 300 DPI. Only the printed size changes: more DPI means a smaller, denser print.
How do I work out the print size?
Divide the pixel size by the DPI. A 3000 by 2000 pixel photo at 300 DPI prints at 10 by 6.67 inches. The same photo at 150 DPI prints at 20 by 13.33 inches with the same pixels spread over a larger area.
Does this tool re-compress my JPG?
No. It edits only the resolution fields in the file header: the JFIF density, the EXIF resolution tags if present, and Photoshop's resolution record if present. The compressed image data is copied byte for byte, so there is no quality loss.
Which formats are supported?
JPEG and PNG. For PNG the DPI is stored in the pHYs chunk, which uses pixels per metre, so 300 DPI is saved as 11,811 pixels per metre and reads back as 299.9994, which programs show as 300. HEIC, WebP, GIF and TIFF files are not supported.
What if my image does not have enough pixels for the print size I need?
Then changing the DPI alone will make it print smaller, not sharper. You would need more pixels, which means resizing or upscaling. Resizing adds pixels by interpolation; it makes a larger file but cannot recover detail the camera never captured.
Is my image uploaded?
No. The file is read and edited in your browser and the new copy is saved straight to your device. Nothing is sent to a server.