Image DPI Checker – Read Embedded DPI from PNG and JPG Files

Read the embedded DPI from PNG and JPEG files and see the print size, free.

What DPI actually means

DPI stands for dots per inch, and it answers a simple question: if you print this image, how big will it be on paper? An image that is 3000 pixels wide, printed at 300 DPI, becomes 10 inches wide. The same image at 72 DPI would claim to be over 41 inches wide, which is why a web graphic looks blurry when printed: it was never meant to be that big.

Here is the catch. Many image files carry no DPI information at all. DPI is metadata, a small note stored in the file header, and plenty of tools never write it. This checker reads that note when it exists, and says so plainly when it does not. Guessing would be worse than admitting the gap.

How to check a file

Choose a PNG or JPEG file and press check. The tool parses the PNG pHYs chunk, which stores pixels per metre, or the JPEG JFIF header, which stores density directly or in dots per centimetre. It converts everything to DPI, shows the pixel size, and calculates the print size at that DPI in inches.

Everything runs in your browser. The file is read locally, nothing is uploaded, and the result appears instantly. There is no account and no waiting.

Reading the result

If the tool reports 300 DPI, you have a print-ready file at that size. A 3000 by 2400 pixel image at 300 DPI prints at 10 by 8 inches, which suits a magazine page or a large photo print. If it reports 72 DPI, the file was probably made for screens; printing it large will look soft, though printing it small, such as a 4 by 6 inch photo, can still look fine.

If the tool reports no DPI info, do not panic. It does not mean the image is bad. It means the file never recorded a DPI value, which is normal for screenshots, phone photos, and web downloads. You can still decide a print size yourself: divide the pixel width by the DPI you want. A 2400-pixel-wide image printed at 300 DPI gives 8 inches, whatever the file says.

Why DPI confuses people

The confusion comes from mixing up pixels and inches. A screen shows pixels; paper shows inches; DPI is the bridge between them. Changing the DPI note in a file does not change the pixels, so it cannot add detail. It only changes the default print size. A 72 DPI file and a 300 DPI file with the same pixels contain the same image; they just suggest different sizes on paper.

That is also why resampling matters. If you need a bigger print, you need more pixels, not a bigger DPI number. Upscaling software can invent plausible pixels, but it cannot recover detail that was never captured. Start from the largest original you have.

Practical print guide

For photo prints, aim for 240 to 300 DPI at the final size. For posters viewed from a distance, 150 DPI is often enough, because the eye cannot resolve fine detail from metres away. For line art and text, 300 to 600 DPI keeps edges crisp. Use this checker to verify a file before sending it to a printer, and you will catch the classic mistake: a beautiful screen image that was never big enough for paper.

Try it with a few files from your own collection. You may be surprised how many carry no DPI value at all, and how useful a plain answer is when you are deciding what can be printed.

One last tip: when a printer asks for a file at a specific DPI, they are really asking for enough pixels at the final size. A quick check here tells you whether your file already qualifies or whether you need the larger original. That single check, done before you send anything, prevents the most common and most embarrassing prepress delay.

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