π¨οΈ Image DPI Changer
Set print DPI metadata for PNG and JPG without touching a pixel.
How to Change Image DPI
Upload a PNG or JPG, enter the DPI you need (300 is the print standard), and download. The tool rewrites only the resolution metadata: the PNG pHYs chunk or the JPG JFIF density fields. Your pixels, colors, and file quality are untouched.
Upload a PNG or JPG file using the file picker.
Type your target DPI or click a preset: 72 for screen, 150 for large format, 300 for quality print.
Click Set DPI and Download. The tool shows the new print dimensions at your chosen DPI.
DPI vs. Pixels: What Really Matters
DPI is one of the most misunderstood numbers in imaging. Your image is a grid of pixels, and DPI only records how tightly a printer should pack those pixels onto paper. A 3000 by 3000 pixel image contains exactly the same detail at 72 DPI and 300 DPI: the difference is purely the intended physical size, 41 inches versus 10 inches square. Screens ignore DPI completely; a 1000-pixel-wide image looks identical on a monitor whether it is tagged 72 or 300 DPI. This is why "increasing DPI" in a metadata tool never sharpens anything, and why anyone promising sharper prints from DPI alone is mistaken. Real print sharpness comes from pixel count: for a target print size in inches, multiply by your desired DPI to get the pixels you need. An 8 by 10 inch print at 300 DPI needs 2400 by 3000 pixels. If your file is smaller, you must either accept a smaller print, a lower DPI, or upscale the pixels first (see our Image Enlarger), understanding that upscaling invents detail rather than recovering it.
How the Metadata Is Written
PNG stores resolution in the pHYs chunk as pixels per unit, with unit 1 meaning meters. The tool converts your DPI to pixels per meter (DPI times 39.3701), then inserts or replaces the pHYs chunk right after the IHDR chunk, recalculating the CRC32 checksum so the file stays valid. JPG stores resolution in the JFIF APP0 segment: two bytes each for X and Y density plus a units byte, where 1 means dots per inch. The tool locates the APP0 marker, sets units to 1, and writes your DPI into both density fields. Both operations are byte-level edits: no decoding, no re-encoding, zero quality change, and the rest of the file is preserved exactly. The result opens in every standard viewer and is honored by Photoshop, InDesign, and print RIPs.
Frequently Asked Questions
What does DPI actually change in my image?
DPI is metadata that tells printers how densely to place the pixels on paper. Changing it does not add, remove, or alter a single pixel: your image keeps its exact pixel dimensions and quality. What changes is the physical print size. A 3000 by 2400 pixel image prints at 10 by 8 inches at 300 DPI, but at 41 by 33 inches at 72 DPI.
Which formats are supported?
PNG and JPG. For PNG, the tool writes the pHYs chunk with pixels-per-meter derived from your DPI value. For JPG, it updates the JFIF APP0 header density fields and sets the units to dots per inch. Other formats like WebP and GIF have no standard DPI storage that this tool writes, so they are not supported.
Will this make my image print sharper?
Only if the pixel data supports it. DPI metadata cannot create detail that is not there. A 600 by 600 pixel image set to 300 DPI prints a sharp 2 by 2 inches, but printing it at 8 by 8 inches from the same file will look soft no matter what the DPI tag says. For crisp prints, you need enough pixels: multiply your target print inches by 300.
Why do print shops ask for 300 DPI?
300 dots per inch is the long-standing standard for quality offset and digital printing because at normal reading distance the human eye cannot resolve individual dots at that density. Large-format prints viewed from farther away can use 150 or even 100 DPI. Screens ignore DPI entirely and only care about pixel dimensions.
Is my image uploaded to a server?
No. The file is read into memory in your browser, the header bytes are rewritten with JavaScript, and the modified file downloads directly. Your images never leave your device, which is important for client work and unreleased designs. The rewritten file stays byte-identical except for the resolution fields.
How can I check the DPI after converting?
On Windows, right-click the file, choose Properties, then the Details tab, where horizontal and vertical resolution are listed. On Mac, open in Preview and press Cmd+I. In Photoshop, Image Size shows the resolution with resampling off. All should reflect the value you set.