If an uploaded image is oversized by a large degree, the Image Properties popup will provide a warning about this and prompt to use the crop wizard.
Note: The editor does its best to replicate the image dimensions as they appear in the live website, in some cases due to the template code, this may not be 100% accurate so please use as an indicative guide.
If you want to get an understanding of an elements dimensions, you can use the Style Editor (RED COG icon) to get an approximate size. (SIZE EST). You can also view image properties via the Image Settings (RED CHAIN) icon.
With image properties you get the estimated size area along with the images original dimensions.