Free Online Image DPI Converter
Change the DPI metadata of an image for print requirements.
Load a PNG or JPEG to read its current print resolution.
DPI is metadata: it tells a printer how large to place the image. Changing it does not add,
remove, or resample a single pixel. The tool rewrites the PNG pHYs chunk or the JPEG
JFIF density fields directly, so image data stays byte-for-byte identical.
About the Image DPI Converter
DPI, or dots per inch, is one of the most misunderstood numbers in digital imaging. It does not describe how sharp a photo is, and it does not change how many pixels the file contains. It is a print instruction: given a certain number of pixels and a chosen density, the printer calculates how many inches the picture should cover on paper. This tool changes that instruction inside the file without touching the actual image. A 3000-pixel- wide photo at 300 DPI prints ten inches wide; the same file at 150 DPI prints twenty inches wide with the same pixels spread over twice the distance.
Metadata, not resampling
For PNG files the tool locates the pHYs chunk and rewrites its pixels-per-metre values along with
the unit flag. For JPEG files it finds the JFIF application segment and updates the density units and X/Y
density fields. Everything else in the file is copied through unchanged, which means the compressed image data,
color profile, EXIF information, and transparency survive exactly as they were. If a JPEG has no JFIF segment,
a new one is inserted immediately after the start-of-image marker.
Why print size changes while pixels do not
A printer receives two independent facts: how many pixels exist and how densely they should be placed. Changing the second leaves the first alone. This is why a small file cannot become a high-resolution print just by typing 600 DPI. It can become a smaller print at the same pixel count. To genuinely add detail you must resample upward, and even then the software can only interpolate new pixels rather than recover information that was never captured.
Other formats
WebP, GIF, AVIF, and BMP files do not use the same simple density fields. For those inputs the tool draws the image at its original dimensions onto a canvas and encodes a PNG or JPEG copy, then writes the requested DPI into that new file. The pixel dimensions are preserved, but re-encoding a lossy source adds one more generation of compression. When exact metadata preservation matters, start from a PNG or JPEG.
Frequently asked questions
Does changing DPI improve image quality?
No. It only changes the instruction a printer uses to scale the image on paper. The pixel grid and the amount of detail stay identical.
How do I calculate the print size?
Divide the pixel width by the DPI to get inches, and divide the pixel height by the DPI for the other dimension. For example, 3000 × 2400 pixels at 300 DPI is 10 × 8 inches.
Will my editing software show the new value?
Most applications that read PNG or JFIF metadata will show the new density immediately. Some editors ignore embedded DPI and use their own export setting, so check the value in the print dialog if it matters.