A print shop, a publisher, a passport photo service or an online form asks for a picture “at 300 DPI”. You right-click your photo, look at its properties, and it says 72 dpi, or 96. The good news is that this is usually a label, not a quality problem, and changing it takes seconds without touching the picture. The catch is that a photo can carry that label in more than one place, and different programs read different ones.
The short answer
- In the browser: drop the photo on Change Image DPI, keep 300 selected, and download. It rewrites every DPI record in the JPG or PNG and leaves the pixels byte for byte as they were.
- Photoshop: Image > Image Size, untick Resample, type 300 in Resolution, save.
- Mac Preview: Tools > Adjust Size, untick Resample image, set the resolution to 300 pixels/inch, save.
- GIMP: Image > Print Size, set X and Y resolution to 300, then export.
The word that matters in all of them is Resample. With resampling off, only the DPI number changes and the photo prints smaller and sharper. With it on, the program invents or throws away pixels to keep the print size, which is a different job. Editors also save the JPG again when you export, which compresses it once more; the browser tool does not re-save the pixels at all.
Why your photo says 72, or 96, or something else
A JPG can store its resolution in the JFIF header at the start of the file, in the EXIF data that cameras and phones write, or in
neither. Windows takes the EXIF value first and uses 96 when it finds no usable value; Python’s widely used image library,
Pillow, takes the JFIF value first. We opened eight real photos from cameras and phones (from the public
exif-samples collection) with both, in October 2026:
| Camera or phone | Stored in the file | Windows shows | Pillow shows |
|---|---|---|---|
| Canon EOS 40D | JFIF 72, EXIF 72 | 72 | 72 |
| Panasonic DMC-FZ30 | JFIF 72, EXIF 72 | 72 | 72 |
| Sony HDR-HC3 | JFIF 72, EXIF 72 | 72 | 72 |
| Nikon D70 | JFIF 240, EXIF 240 | 240 | 240 |
| Pentax K10D | JFIF 350, EXIF 350 | 350 | 350 |
| Nokia 8.3 5G phone (2 photos) | No DPI at all | 96 | 72 |
| Jolla phone | EXIF 72 without a unit | 96 | 72 |
None of these numbers says anything about quality. 72 and 96 are leftovers from old screen conventions, and the two phones did not record a resolution at all, so each program filled in its own default. That is also why two people can look at the same file and report different DPI.
The trap: changing one record and not the other
Because there can be two records, a tool that changes only one leaves the other behind. We built test files to see what happens. A photo with EXIF 72 whose JFIF header was changed to 300 still showed 72 dpi in Windows File Explorer, while Pillow said 300. The opposite file, EXIF 300 and JFIF 72, showed 300 in Windows and 72 in Pillow. If a print shop’s upload page reads the record your tool did not change, it rejects a file you thought you had fixed.
So after changing the DPI, check it in the place that matters to you, and if you can, use a tool that writes both records. Change Image DPI lists every record it finds before it changes anything, writes them all, and reads the saved file again to show they match.
How to check the DPI
- Windows: right-click the file, Properties, Details tab, Horizontal resolution.
- Mac: open it in Preview, Tools > Show Inspector; the first tab shows the image DPI.
- Any device: drop it on Change Image DPI; it reports the JFIF, EXIF, Photoshop and XMP values separately and says which one Windows shows.
Is 300 DPI enough? Check the pixels
“300 DPI” on its own means nothing without a print size. What the printer actually needs is enough pixels: 300 for every inch of paper. Divide the photo’s width and height in pixels by 300 to get the largest size it prints sharply:
| Print size | Pixels needed at 300 DPI | A 12-megapixel phone photo (4032 × 3024) |
|---|---|---|
| 2 × 2 in passport photo | 600 × 600 | Plenty |
| 4 × 6 in | 1200 × 1800 | Plenty |
| 8 × 10 in | 2400 × 3000 | Enough |
| A4 (8.27 × 11.69 in) | 2480 × 3508 | Just enough |
| 11 × 14 in | 3300 × 4200 | Short: about 13.4 × 10 in at 300 |
A picture saved from a website or a messaging app is often only 800 to 1600 pixels wide. Set to 300 DPI, a 1200-pixel-wide image prints 4 inches wide; stretched to fill a page it will look soft, whatever the label says. In that case you need the original, larger file, not a different DPI.
On an iPhone
The Photos app has no DPI setting, and iPhones save photos as HEIC by default, which most print services and forms do not accept. Convert the photo to JPG first with HEIC to JPG (or set Settings > Camera > Formats to Most Compatible for future photos), then open Change Image DPI in Safari and set 300. Both run in the browser on the phone; the photo is not uploaded.
Quick answers
Does changing 72 DPI to 300 DPI improve quality? No. The pixels stay the same; only the print size changes. The same photo simply prints at about a quarter of the width.
Will changing the DPI make the file bigger? Not when only the label changes: in our tests the file grew by 0 to 21 bytes. If a program makes the file much larger or smaller, it resampled or re-compressed the picture.
A form wants 300 DPI and under 200 KB. What do I do? Resize or compress first, for example with Resize Image, then set the DPI last: some compressors drop the DPI record when they save.