Getting an irregular-shaped object's pixel area in Photoshop

Is there a way to get an oddly-shaped object's pixel area in CS5? Eg. Circle/ellipse. Or, if there's some easy-to-automate way to do it outside of Photoshop.

I know it's possible to use a magic wand selection and see the height+width 开发者_高级运维in the info panel, but that only works accurately for rectangles.

Thanks!!

Double click the layer thumbnail in the layers list

This will select the shape of pixels in the layer.