DPI checker — read an image's DPI and see how large it will print

How to use the DPI checker

1. Choose a JPEG or PNG image.
2. Optional: enter Planned print width (0 = skip) in centimetres.
3. Optional: tick Also save a copy with a new DPI value and set New DPI (1 to 2400).
4. Press Check DPI. Read the results: Embedded DPI, Stored in, Pixels and Print size at that DPI, then the table of sizes. If you asked for a copy, download it at the top.

What it does and when to use it

DPI (dots per inch), or PPI for pixels, links pixels to paper. What matters for a print is how many pixels land in each inch:

pixels per inch = pixel width ÷ print width in inches (1 inch = 2.54 cm)

The tool reads the stored value from the JFIF header or EXIF block of a JPEG, or from the pHYs chunk of a PNG. It then tells you how a print of your planned width will look:

Use it before sending photos to a print shop, when an exam or visa form asks for a set DPI, or to find the largest sharp print a photo allows. To change the pixel size itself, use the image resizer. For a general print-resolution calculator, see the PPI and DPI calculator. To see all the other metadata in a photo, try the EXIF reader.

How it works

Everything happens on your device; the file is not uploaded. The tool reads the file header without decoding the picture. When you ask for a new DPI, it rewrites only the resolution field: the JFIF header of a JPEG (adding one if missing) or the pHYs chunk of a PNG. The image data is copied untouched, so there is no quality loss. The copy is named like photo-300dpi.jpg.

Worked examples

These figures come from the tool’s own calculation.

• A 3000 × 2000 camera photo labelled 72 DPI. Print size at that DPI: 105.83 × 70.56 cm. The table shows the same pixels at 300 DPI as 25.4 × 16.93 cm (10 × 6.67 in). Both are the same photo; only the label differs.
• The same photo, planned print width 20 cm. 3000 ÷ (20 ÷ 2.54) gives 381 pixels per inch: “excellent for close viewing”.
• A 1200 px wide image, planned width 20 cm. About 152 pixels per inch: “acceptable for posters viewed from a distance”. For a sharp 300 DPI print, 1200 px covers 4 inches (10.16 cm), the short side of a 4 × 6 inch photo.

Limits and tips

• Only JPEG and PNG are read. Convert other formats first.
• More DPI on the label cannot add detail. If a print needs more pixels than you have, use a smaller print size.
• Sizes in the table are rounded to two decimal places.