They'll all be the same size as the image :- Image --> Image Size.
You could turn off (remove the eye on the layers pallete) all the layers except the one you want to see and use the measuring guides to get the size of an object on a layer (i.e. - box, image).
or crop the image temporarily to the dimensions of the layer, and check out the image size.
But, to answer your very legitimate question, as far as i know Photoshop is not intelligent enough to tell you the size of an object in an otherwise-transparent layer. Seems like a pretty reasonable favor to ask of it though, right?
Here's how I check the dimensions in a layer:
select your layer
choose select all (command-a)
highlight the selection in the layer by choosing command-up arrow
view selection dimensions in the info window.
Make sure that you replace the selection to its original position before exiting by using command-down arrow or you will have permanently moved the selection up 1 pixel
I've developed an almost instinctive method for this...
Almost the same as mentioned above, but I don't like mouse clicks.
Make the layer current
Press up arrow
Press down arrow
Press control+n (on PC)
The new document dialog will tell you the dimensions.
simple solution: Make sure you can see the Info pallete (Window, Info) and the Layer pallette (Window, layers)
Select your layer in the Layer pallette, then Hold Ctrl and click on that layer
You will see W:? H:? in the Info pallete, thats your dimensions.
good shortcut, however I must mention one thing:
On a Mac it's not the control key, it is the command key also kown as the apple or cloverleaf key. The control key is like using right-click on a pc.
But I must confess that having used PS for about 10 years I did not know if this short cut .... thanks!
sorry about that travelin cat..
Not used a mac in a while and had forgotten about them.. Anyhow, glad you figured it out ;)
10 Years eh, same here.. but I am still learning something new about photoshop every week.