Image DPI Converter

Print shops, publishers and online forms often ask for images “at 300 DPI”. The request causes endless confusion, because a digital image has no physical size by itself. It has pixels, plus a stored number that suggests how many of them belong in one inch when printed. This tool changes that number, or resizes the image for a specific print size.

What DPI really means

DPI, or more precisely pixels per inch for digital images, connects pixels to physical size. An image 3000 pixels wide prints 10 inches wide at 300 DPI, or 41.7 inches at 72 DPI. The pixels and their detail are identical in both cases; only the print size differs. The stored DPI value is a hint that layout programs such as Word, InDesign and many print services use to decide the default size.

Change DPI only

The first mode rewrites the stored resolution and keeps every pixel unchanged. For JPG files, the density in the JFIF header and the resolution fields in EXIF are updated; for PNG, the pHYs chunk. The image data is not decoded or re-compressed, so there is no quality loss at all. Other formats are converted to PNG with the new value.

Resize for a print size

The second mode changes the pixels. Enter the print width in centimeters or inches and the resolution, and the image is resampled to exactly the number of pixels that gives that size. Use it to prepare an image for a specific frame or layout, or to reduce a huge image to what a printer actually needs. Enlarging this way does not add detail; for that, see Upscale Image.

How much resolution is enough

For photo prints viewed in the hand, 300 pixels per inch is the standard. Posters seen from a few meters away look fine at 150. Large banners and billboards often use 30 to 100. Newspapers print at around 200. Screens ignore DPI entirely and show images by pixel count.

What forms actually check

Online portals that ask for a certain DPI usually read the stored value, and sometimes the pixel dimensions. If a passport or visa portal rejects a photo for DPI, setting the value here is usually the fix. If it rejects it for pixel size, the image needs resizing, not a new DPI value.

Quick calculations

Pixels equal inches times DPI. Inches equal pixels divided by DPI. To convert centimeters, divide by 2.54 for inches. A 10 × 15 cm print at 300 DPI needs about 1181 × 1772 pixels.

Privacy

All changes happen in your browser; images are not uploaded.

Why 72 DPI keeps appearing

Many cameras, phones and screenshot tools write 72 DPI into files by default, a value inherited from early Mac displays. It means nothing for quality. A 4000-pixel photo marked 72 DPI is just as detailed as the same photo marked 300 DPI; it would only be placed larger by default in a layout program.

Setting DPI for a batch

When a print shop asks for a whole set of images at a certain DPI, change each file here; the pixels and quality remain identical, and the files are ready for upload in seconds.

Related tools

For passport and visa photos at exactly 300 DPI with correct dimensions, use the Passport Photo Maker. To set exact pixel dimensions, the Image Resizer is simplest. For converting pixel and print units, the Unit Converter helps.