"Check the DPI" sounds like it should be a one-click answer, but most images don't actually carry a DPI number the way you'd expect — and the method that works depends entirely on what device or software you're using. Here's every reliable way to find it, on Mac, Windows, in Photoshop, and without installing anything at all.
On Mac, open the image in Preview and use Tools → Adjust Size to see its resolution. On Windows, right-click the file → Properties → Details tab, and look for Horizontal/Vertical Resolution. In Photoshop, use Image → Image Size and read the Resolution field. If you don't have any of those, a free online DPI calculator reads the pixel dimensions in your browser and works out the DPI at whatever size you plan to print — no software or upload needed. Many images (especially screenshots and web downloads) don't carry a real DPI tag at all, which is normal, not an error.
Why "Checking DPI" Is Trickier Than It Sounds
DPI (dots per inch) isn't a fixed property of an image the way its pixel dimensions are. It's a label — a small tag stored inside the file — that tells a printer how densely to pack the pixels onto paper. A photo can have exactly the same pixels and be tagged 72 DPI, 150 DPI, or 300 DPI, and all three tags describe the identical file printed at different physical sizes.
That's why "check the DPI" sometimes returns a number, and sometimes returns nothing useful at all — a screenshot or a web-exported PNG frequently has no real DPI tag, or defaults to 72, regardless of how many pixels it actually contains.
Pixel dimensions (e.g. 3000 × 3000px) are the real, fixed thing. DPI is just a printing instruction layered on top. If you know the pixel dimensions and the size you want to print at, you can always calculate the DPI yourself — which is exactly what a DPI calculator does.
How to Check DPI on a Mac
Open the image in Preview
Double-click the image, or right-click → Open With → Preview.
Open the size panel
Go to Tools → Adjust Size (or Tools → Show Inspector on some macOS versions). This panel shows the image's current resolution alongside its pixel dimensions.
Read the resolution field
The number shown (in pixels/inch) is the file's stored DPI value. If "Resample image" is unchecked, you can also change the physical print size here and watch the resolution recalculate live, which is a fast way to see what DPI you'd get at a specific print size.
Finder's regular Get Info panel (Cmd+I) shows pixel dimensions but not DPI directly on most macOS versions — use Preview's size panel instead, not Get Info, if DPI specifically is what you need.
How to Check DPI on Windows
Right-click the image file
In File Explorer, right-click the image and choose Properties.
Open the Details tab
Click the Details tab in the Properties window.
Find Horizontal/Vertical Resolution
Scroll to the Image section and look for "Horizontal resolution" and "Vertical resolution" — these are shown in DPI. For most consistent files the two numbers match; if they don't, or the fields are blank, the file likely doesn't carry a DPI tag at all.
How to Check DPI in Photoshop
Open the file
File → Open, or drag the image into Photoshop.
Open Image Size
Image → Image Size (or Option/Alt+Ctrl+I).
Read Resolution
The Resolution field shows pixels/inch directly, right alongside the pixel dimensions and the physical document size. This is the most reliable method of the three, since Photoshop reads the file's actual embedded metadata rather than inferring anything.
In that same Image Size dialog, unchecking "Resample" lets you type a target print size and watch the resolution recalculate instantly — the fastest way in Photoshop to answer "what DPI would this be at 8×10 inches?" without leaving the dialog.
No Photoshop, No Design Software? Use a Free Online Checker
Not everyone has Photoshop installed, and digging through Windows Properties or Mac Preview panels is more steps than it needs to be for a quick check. A free DPI calculator does the same job from a browser:
Drop the image in
The tool reads the image's pixel dimensions in your browser using the standard Image API — the file itself is never uploaded to a server.
Get the biggest print size at 300 and 150 DPI automatically
Rather than just reporting a stored (and often meaningless) DPI tag, the calculator works out the largest size you can print the image at 300 DPI (sharp, close-up viewing — posters, framed art) and at 150 DPI (fine for large-format prints viewed from further away, like banners or big canvases), in both inches and centimetres.
What to Do If the DPI Is Too Low
Finding out your DPI is low is only useful if you know what to do next — and the fix depends on why it's low:
If the pixel count is actually fine, just fix the tag
Sometimes an image has plenty of pixels for the print size you want, but is tagged at 72 DPI anyway — common with screenshots and web-exported files. In that case nothing is actually wrong with the image; Change DPI edits just the stored tag (the PNG pHYs chunk or JPG JFIF density field) without touching a single pixel, so there's no quality loss.
If the pixel count is genuinely too small, upscale first
If the image doesn't have enough real pixels for your target print size — say, a 1000px design that needs to be 3000px for a sharp 10×10in print — changing the DPI tag alone won't fix it, because DPI doesn't add or remove pixels. Run it through the AI Image Upscaler first to rebuild detail and hit the pixel count you actually need, then set the DPI tag afterward.
Changing a DPI tag never makes an image sharper on its own — it only relabels how many of the existing pixels should fit per inch. If the image looks soft at full size on screen, it will still look soft printed, regardless of what the DPI number says.
Check Your Image's Real Print Size in Seconds
Drop in any image and see instantly what size it can print at 300 DPI and 150 DPI — free, no sign-up, nothing uploaded.
Check My Image's DPI →