Image DPI Checker & Changer
See the DPI written in a JPEG or PNG and how big that prints, then save it with the DPI a print shop asks for. Your photo never leaves your device.
The DPI written in the sample
Not set
Its JPEG header says "no units": that only says the pixels are square, so it sets no DPI and each program picks its own (macOS shows 72).
- 900 × 562 pixels, a JPEG
Saved at 300 dpi, it prints 3 × 1.87 in (7.62 × 4.76 cm). Not one pixel changes, so neither does the detail: to print bigger at 300 dpi, you need a picture with more pixels.
Where a file keeps its DPI: JFIF 1.02, Exif's resolution tags and Photoshop's own, and the PNG pHYs chunk. Checked 27 September 2026.
Quick answer: A photo's DPI is only a number written inside the file. It tells a printer how many of the photo's pixels to fit into each inch. Choose your JPEG or PNG above to see the number and how big it prints. Then save it with the DPI a print shop asks for, usually 300. Changing it moves no pixels and adds no detail. It only changes the size the photo prints at. The photo is read and saved in your browser and never uploaded.
How to use it
- Choose your photo, a JPEG or a PNG. It is read on your device, not sent anywhere.
- Read what it says. The DPI written in the file, where it is written, and the size that prints at. Some files write it in two places that disagree. The tool shows both.
- Type the DPI you need (300 is what print labs call standard) and tap "Save it". You get the same photo back, every pixel the same, with the new number in every place the file keeps one.
Where a photo keeps its DPI
- A JPEG's JFIF header. The JFIF 1.02 standard gives it a units byte: "units = 1: X and Y are dots per inch", "units = 2: X and Y are dots per cm". With "units = 0: no units, X and Y specify the pixel aspect ratio", no DPI is set at all, whatever the numbers say.
- Exif, the block cameras and phones write: its XResolution, YResolution and ResolutionUnit tags.
- Photoshop's own block (its ResolutionInfo), which Photoshop reads first.
- A PNG's pHYs chunk. The W3C PNG standard counts "Pixels per unit" where "1 unit is the metre", so 300 DPI is written as 11,811 pixels per metre. Some PNGs also carry an Exif block.
Programs do not agree on which one to read first. That is why a photo can show 72 in one app and 300 in another. The changer writes the same number in every place the file has.
Does changing the DPI make a photo better?
No. A 900 × 562 photo has 900 × 562 pixels at 72 DPI and at 300 DPI. What changes is how big it prints: 12.5 inches wide at 72, 3 inches wide at 300. A print shop that asks for "300 DPI" wants enough pixels for your print size at 300 per inch. For a 4 × 6 in print that is 1200 × 1800 pixels. The pixels to inches & DPI calculator works that out for any size and quotes what two print labs say.
72 DPI, 96 DPI and screens
A screen ignores the number. A web page and a Pinterest pin show a picture by its pixels. That is why so many files say 72, or nothing at all: the number never mattered until someone wanted to print. When a file sets nothing, each program picks its own. macOS shows 72, as we checked on the sample here.