Finding Size of Disk Allocation Table

Not sure where to post this but here will do.

I have an exam 2morro and one of the possible questions is to find the size of the Bit Table being used to implement a disk allocation table. Fairly Basic i know but i cant seem to remember how to do it.

Here is a sample question that could come up.

In an operating system that uses a Bit Table to implement a Disk Allocation Table to record space allocation on the disk (Used space & free space), what size will the Bit Table be(in bytes) assuming there are 500,000 blocks on the disk of which 200,000 are currently used?

Any help would be greatly appreciated

 

In case if you were referring to the File Allocation Table, this link might be helpful:

http://www.pcguide.com/ref/hdd/file/part_Sizes.htm

 

No that page only tells me what the size of the clusters are. I need to find out what size the actual table is going to be.