Layer Size Help??

This may be a dumb question, but it's driving me nuts. Is there a way to figure out the size of a layer object inside an image in PS?

For example, you draw a square in your image as a placeholder, and you resize it to what you want on the page. How big is it? Later you want to add an image the exact size of that box. How do you know what size to make the image?

I can't find this in help anywhere, everything is about the entire bigger image sizing, not the sizes of individual layer components. Is there a place to see the size of something on a specific layer, not the entire image?

Thank you so much for any help!!

The info pallet will show the size of any selected object, you can use the rule tool under the eyedroper tool

you can also resize most things from the menu- transform- scale just type the size you want in the boxes

Thank you thank you!

I didn't know the resize under transforms was for objects, thought it too was for the entire page! Really appreciate it:)!