PowerPoint can automatically resize an image to fit a shape. You can also resize several images that are already in your presentation to the same size. This is how it works.
Automatically resize an image that fits a shape
First, continue and open a new PowerPoint presentation and insert a new frame with a content box in it. You can do this by clicking "New Image" on the "Insert" tab and selecting one of the image templates. We choose "Title and Content" in this example. You can also insert a content box or form into an existing image.
Next, resize the content box by clicking and dragging the corners.
When you are satisfied with the size, click the "Images" icon.
Place the image you want and click "Insert."
PowerPoint changes the image to fit the content box.  Change multiple images to the same size
Suppose you already have several pictures and that they are all different sizes. To make them equal, first select all images by holding ctrl and clicking on each image in turn.
Go to the "Format" tab under "Picture Tools".
At the top of the group "Size" you specify the height and width you want for the images.
When writing a number in either the Height or Wide, the second box will automatically enter a proportional number. When done, press Enter.
Resize multiple images at one time
If you have images of different sizes in the picture and you don't want to make them the same size, but you want to resize them at once , select all images by holding Ctrl and clicking on each image in turn. Once you have chosen, grab the corner and drag the pictures.
Although we understand that there are always faster ways to achieve certain tasks, we want to show that there are different ways to handle them. Although it may be simple enough for you to simply insert an image and resize it after it has been inserted, it is always good to know your options.