whos will work if you want the memory consumption of any variable including its metadata.
A=rand(10);
whos A
Note that this doesn't distinguish between deep and shallow copies. So, for example, in the code below, B is not really consuming an additional 800 bytes of memory on top of what A consumes (because it is just a shallow copy of A).
B=A;
whos A B
However, if you were to modify B in any way, Matlab would allocate B it's own 800 bytes.
