The option for finding your image size in Adobe Illustrator isn't as obvious as in its sister program, Adobe Photoshop. Illustrator offers no "Image" option in its menu bar and no convenient "Image size" option within that menu. It does, however, specify the precise size of the artboard, which is the printable area that includes the image. Remove the blank portions of the artboard to make its size equal to that of the image, letting you check the size of both.
Press the "M" key to select the Rectangle Tool.
Click one corner of your image and drag to create a rectangle that covers the image.
Press the "Shift" and "O" keys to select the Artboard Tool.
Double-click the rectangle. The artboard will shrink to the size of the rectangle, which is also the size of the image.
Double-click the "Artboard Tool" icon from the toolbar. This opens the Artboard Tool dialog box.
Read the artboard's width and height from the dialog box. These are the image's dimensions.
Press the "Ctrl" and "Z" keys to undo all of your actions, reverting the artboard's size and deleting the rectangle.