Are your email signature images changing size or showing much larger when you install the signature in your email client?

The most common reason for email signature images changing in size is because the image resolution (in DPI) is not set to 96 DPI for Outlook, or 72 DPI for Apple Mail.

If your DPI settings are too high, you’ll likely end up with an enlarged image in your email signature. This happens because Microsoft Outlook and Apple Mail scale images using the DPI value.

To fix this, you will need to use an image processing tool such as Photoshop to change the DPI setting on the image.

Lets take a look at what DPI is and how you can fix this issue.

What is DPI?

DPI stands for Dots-Per-Inch. Also referred to as PPI or Pixels-Per-Inch. It is used to measure how many dots (or pixels) will be used in a line which is 1 inch in length.

pixels per inch explainer

DPI is primarily used to determine the quality of a document which is going to be printed. However, some email clients, mainly Outlook and Apple Mail use DPI to measure the resolution of images, instead of simply using the height and width of the images.

Image DPI Recommendations for Email Signatures

In order for the images in your email signature to display correctly, you will need to use the following DPI settings depending on which email client you’re using.

  • If you’re using Microsoft Outlook, the DPI of the image should be 96 DPI.
  • If you’re using Apple Mail, the DPI of the image should be 72 DPI.

If you have an image in your signature that has a DPI of lets say 300, the image will probably look very big.

How to Check the DPI of Your Images

The simplest way to check the DPI of an image in Windows is to right click on the image > Properties > Details tab, and check the DPI value.

Note: This method only works on some image types and will not work on PNG images.

You can also check and also change the DPI of an image using almost any image processing software, such as Photoshop.

How to Change the DPI of an Image Using Photoshop

Step 1

Open your image in Photoshop.

Step 2

Click on Image > Image Size.

Step 3

In the Resolution field, enter the new DPI value that you want to use (96 DPI for Outlook or 72 DPI for Apple Mail) and ensure that the measurement is set to “Pixels/Inch”.

Also, ensure that Resample: Automatic is ticked.

Step 4

Save your image and use it in your email signature.

Now that the DPI has been changed, this should stop it from scaling up in size.

Other Ways to Change the DPI of an Image

If you dont have Photoshop or any other image processing software, you can easily change the DPI of your images using Clideo or Convert Town, both of which are free tools.