How to check the DPI of an image on Windows and Mac

The DPI of an image is a number stored inside the file. To see it on Windows, right-click the file, choose Properties, open the Details tab and look for the horizontal and vertical resolution. On a Mac, open the picture in Preview and choose Tools > Show Inspector. On any device, drop the file on the image DPI checker, which shows the stored DPI, the pixel size and the size the image prints.

The number on its own does not tell you whether the picture will print well. The pixels do. The last part of this guide shows how to read the two together.

(If you are looking for the DPI of a mouse, that is a different thing: how far the pointer moves for each inch the mouse travels. This page is about picture files.)

On Windows

1. Find the image in File Explorer.
2. Right-click it and choose Properties.
3. Open the Details tab.
4. Scroll down to the image’s Dimensions, which is the size in pixels, and its resolution, which is the DPI.

These are the steps Adobe gives in its guide to DPI: “Right-click on the image file and select Properties. Click the Details tab at the top bar. Scroll down to find image Dimensions and the DPI Resolution.” Expect two resolution figures, one horizontal and one vertical, usually the same number. Windows keeps them as two properties: Microsoft’s documentation lists System.Image.HorizontalResolution, “the number of pixels per resolution unit in the image width”, and a matching vertical property for the height.

Adobe’s guide to PPI describes a second route through the Windows Photos app: open the picture, click the three dots at the top, choose File Info, and look under Size Info.

On a Mac, with Preview

1. Open the image in Preview. From the Finder, right-click the file and choose Open With > Preview.
2. Choose Tools > Show Inspector.
3. Look at the first pane, General Info. The line Image size is the size in pixels and the line Image DPI is the resolution, in pixels/inch. Adobe’s guide adds that the More Info pane, the second tab, also lists the DPI.

Apple’s Preview guide says the Inspector window shows “information about a document or image, such as file size, the author name, and the image resolution”, with a General info pane and a More info pane (View information about PDFs and images in Preview).

To see what the number does to the print size, choose Tools > Adjust Size. The dialogue shows the width, the height and a Resolution field together. Press Cancel when you have looked, so that nothing is changed.

On a Mac, in Terminal

macOS includes a command called sips that reads the same value:

sips -g dpiWidth -g dpiHeight -g pixelWidth -g pixelHeight photo.jpg

It prints the path of the file and then four lines, for example dpiWidth: 300.000 and pixelWidth: 1200. Tested on macOS 26.6 with PNG and JPEG files saved at 72 and at 300 DPI, it reported each correctly. For a PNG that stated no resolution at all it printed dpiWidth: 72.000, so a 72 from sips can also mean that the file says nothing. It is the fast way to check a folder of files: put *.jpg in place of the file name and it lists every one.

In Photoshop

Choose Image > Image Size and read the Resolution box. Adobe’s note is to select Pixels/Inch in the drop-down beside it. Close the dialogue without changing anything.

In GIMP

Choose Image > Image Properties, or press Alt + Return. The Properties tab lists “Size in pixels”, “Print size” and “Resolution”, which the GIMP 3.0 manual describes as “the print resolution of the image”. GIMP sometimes shows the resolution of a PNG in pixels per millimetre: 11.811 pixels/mm is 300 DPI. More in GIMP DPI.

In your browser, on any device

The image DPI checker reads a PNG or a JPEG without uploading it. It shows four things:

• Pixels: the real size of the picture.
• DPI in the file: the resolution the file states, and where in the file it was found.
• Prints at: the pixels divided by that DPI, in inches and centimetres.
• At 300 DPI: the largest size the picture prints at photo quality.

It works the same on a phone, where there is no Properties window to open.

What the number means

The stored DPI is an instruction about size: print this many of my pixels in each inch. It is not a measure of sharpness.

print size in inches = pixels ÷ DPI

Pixels	Stored DPI	Prints at
1200 × 1800	72	16.7 × 25 inches
1200 × 1800	300	4 × 6 inches
4000 × 3000	72	55.6 × 41.7 inches
4000 × 3000	300	13.3 × 10 inches

The first two rows are the same picture, and so are the last two. Change the stored DPI and the pixels do not change at all. This is easy to prove: two PNG files written from the same pixels, one tagged 72 and one tagged 300, decode to identical data.

If there is no DPI, or it says 72 or 96

Many files state no resolution. Others carry 72 or 96 because the camera, phone or screenshot tool writes that by default, and software that finds nothing assumes one of those two. None of this is a fault, and it says nothing about the quality of the picture.

Is the image good enough to print?

Ignore the stored number and work from the pixels:

1. Read the size in pixels.
2. Divide each side by the size you want to print, in inches. That is the DPI you will actually get.
3. Compare it with what the print needs: about 300 for a photo or a page held in the hand, about 150 for a poster seen from a step away.

A 3000 × 2400 pixel photo printed 10 inches wide gives 300 pixels to the inch. Printed 20 inches wide it gives 150. Whatever DPI is written in the file, those are the true figures. What DPI for printing has the thresholds, and the DPI calculator turns any print size into pixels.

If a printer or a form demands 300 DPI

Two different things can be meant.

• The stored number must read 300. Some upload checks only look at the tag. Change it with the DPI converter, which rewrites the stored value and leaves the pixels untouched.
• The picture must have 300 pixels for each printed inch. This is what a printer means. If the pixels divided by the print size come to less than 300, the image is too small for that size, and changing the tag will not help.

Questions

Why do two programs show a different DPI for the same file? First check that both are looking at the same copy of the file. If the file states no resolution, each program fills in its own default, which is why one may say 72 and another 96.

Does a higher DPI mean a better image? No. More pixels do. A 600 × 400 pixel image tagged 300 DPI is a 2 × 1.3 inch print.

Can I check the DPI of a PDF this way? No. A PDF is a page with pictures placed on it at whatever size the layout chose, so each picture has its own effective resolution. The methods here read picture files.

Do I need to check the DPI of a picture for a website? No. A browser shows pixels and ignores the stored DPI, so only the pixel size matters there. See 72 vs 300 DPI.