Finding the pixel dimensions and print resolution of an image on a Mac takes about ten seconds once you know where to look. MacOS gives you at least three different ways to access this data without installing any software, depending on whether you prefer Finder, Preview, or the terminal.
The Fastest Method: Get Info in Finder
Select your image file in Finder and press Command + I to open the Get Info panel. Under the “More Info” section you will see the pixel dimensions listed as width by height, for example 6000 x 4000. This tells you the total number of pixels in each direction. Multiply the two numbers together and divide by one million to get the megapixel count: 6000 times 4000 equals 24 megapixels.
The Get Info panel also shows the colour space and the file size, but it does not display the embedded print resolution in pixels per inch. For that number you need Preview or the terminal. Note that the file size shown in Get Info is the on-disk size, which for a JPEG will be much smaller than the uncompressed pixel data because JPEG uses lossy compression.
Reading PPI and Full EXIF Data in Preview
Open any image in Preview (double-click or press Space in Finder for Quick Look, then Command + Return to open fully). Go to Tools in the menu bar and choose Show Inspector, or press Command + I while the image is open. The inspector panel shows the pixel dimensions, the colour profile, and the embedded PPI (pixels per inch) value stored in the file header. For most digital camera files this is 72 or 96 PPI by default, though that embedded number does not affect actual print sharpness. What determines print quality is the pixel count divided by the desired print size in inches: a 6000-pixel-wide image printed at 300 PPI produces a 20-inch-wide print.
Preview also surfaces the full EXIF metadata under the inspector’s information tab. You can read the camera model, lens focal length, shutter speed, aperture, ISO, and GPS coordinates if they were recorded. This is useful for verifying what settings produced a particular image without opening a full editing application. If you need to find the resolution of a RAW file such as a CR3, ARW, or NEF, Preview on MacOS Ventura and later can read and display the dimensions of most major RAW formats directly.
Using the Terminal for Precise and Batch Queries
If you need to check many images at once or want a precise readout without opening any application, the terminal is the fastest route. MacOS ships with a command-line tool called mdls that reads Spotlight metadata, including pixel dimensions. Open Terminal (found in Applications / Utilities or via Spotlight with Command + Space) and type:
mdls -name kMDItemPixelHeight -name kMDItemPixelWidth /path/to/your/image.jpg
Replace the path with your actual file path. You can drag the file from Finder into the terminal window to auto-fill the path. The output will show two lines giving the width and height in pixels.
For a batch check of an entire folder, the sips command (Scriptable Image Processing System) is built into MacOS and very fast. To print the pixel dimensions of every JPEG in a folder:
sips -g pixelHeight -g pixelWidth ~/Pictures/folder/*.jpg
Each file in the folder will have its height and width listed in sequence. The sips tool also reports the resolution in DPI and the colour space profile, making it a compact way to audit a folder of images before sending them for print or web export.
What the Numbers Actually Mean for Printing and Web
Pixel dimensions tell you the raw count of pixels. The embedded PPI number in the file is essentially a suggestion to the printer or application about how large to render the image, but it does not change the pixel count or the detail in the file. To calculate the maximum print size at a given quality level, divide the pixel width by your target PPI. At 300 PPI for high-quality printing, a 4500-pixel-wide image prints at 15 inches wide. At 240 PPI, which is acceptable for most photo labs, that same file prints at 18.75 inches. At 150 PPI, which is suitable for large-format display prints viewed from a distance, it prints at 30 inches.
For web use the PPI number is irrelevant: browsers render images based on pixel count relative to the display’s pixel density. A 1200-pixel-wide image appears at a fixed size on screen regardless of whether the embedded PPI is 72 or 300. The only number that matters for web is the pixel count. Understanding this distinction prevents the common confusion of thinking that changing the PPI in Preview or Photos makes a file “higher resolution” for print, when in fact only the pixel count determines the real available detail. If you need to understand how interpolation affects enlargements, that involves actually adding or removing pixels rather than changing the metadata tag.
Common mistakes to avoid
- Confusing file size in megabytes with image resolution in megapixels. A heavily compressed JPEG can be 2 MB on disk but contain 24 megapixels of data. A TIFF of the same image might be 70 MB. The file size is about compression, not pixel count.
- Thinking that changing the PPI value in Preview or an image editor improves the actual resolution. Changing the PPI tag resamples the print output size suggestion but does not add any new pixel data unless you also change the pixel dimensions.
- Using Quick Look (Space bar) and assuming the reported dimensions are the final answer. Quick Look shows a thumbnail preview and its dimensions may reflect the preview layer rather than the full-resolution file. Use Get Info or Preview’s Inspector for the definitive numbers.
- Ignoring colour profile information when checking resolution for print. A file can have correct pixel dimensions but be in sRGB when your print lab requires Adobe RGB, which will affect colour accuracy in the final output.
FAQ
How do I find the resolution of a RAW file on a Mac? Open the RAW file in Preview, then press Command + I to open the Inspector. Preview on MacOS Ventura and later reads dimensions from most major RAW formats. Alternatively, use mdls -name kMDItemPixelHeight -name kMDItemPixelWidth yourfile.raw in Terminal. If Spotlight has indexed the file, it will return the dimensions immediately.
Why does my image show 72 PPI but my camera shoots at high resolution? Most cameras embed a default PPI tag of 72 in their JPEG output because that number is a historical web standard with no bearing on the actual pixel count. Your camera’s true output resolution is determined by its sensor pixel count, not by this tag. A Sony A7R V, for example, produces 61-megapixel files regardless of what PPI value is embedded in the metadata.
Can I batch-check the resolution of hundreds of photos at once? Yes. In Terminal, use sips -g pixelHeight -g pixelWidth /path/to/folder/*.jpg to list dimensions for every JPEG in a folder. For mixed formats including RAW files, mdls with a shell loop or a lightweight tool like ExifTool (installable via Homebrew) can process entire directories quickly and output the results to a text file for review.