raw to qcow2 and size

[cmos486]

I converted disk raw to qcow with the following command:
qemu-img convert-p-O qcow2
and I find that the disk only used 12GB but the file of qcow2 size is 200GB qcow2 (disk size on qemu VM)
Since I can do in order that the file qcow2 occupies 12Gb and not 200gb?

Forgive for my English.

 

[cmos486]

UP.

Thanks