Once I have cropped an image in Lightroom (say to 8x10) then stop my workflow and come back to it later I often don't remember what size I've cropped the image to. When I go to the library module it gives me pixel dimensions but not image size. Is there any way to determine what size I've cropped the image to when I come back to it later? Thanks for any help.
Lightroom crops are to image proportion, not image size. Image size is a display or printing thing, determined by pixel counts and ppi/dpi settings for either the monitor or the printer.
When I go to the library module it gives me pixel dimensions but not image size.
Do you mean that you want the number of cropped pixels? If you press Ctrl-J you can select cropped dimension in pixels to be displayed at the top left of your image. (Or do you mean something else?)