I have a standard. the measurements (length width,depth/height) are
48" long and 12" wide 19" deep(inside)
the vertical depth of the tank actually measures nearly 21" external
I think the confusion created is the width which many often mistake as depth.
Those are the dimensions as I understood it.
I tend to think of it as length x depth x height...for some odd reason.
Either way, a 12"+ long oscar is not going to be comfortable turning around in a tank that only allows 12" of room to do so.