How do read blocks in filesystem? What is the conversion to bytes to block or vice versa?

if i had to guess just by looking at the information that i see in a fdisk -l command i would say that you multiply the amount of blocks by 2 and then multiply that number by 512, to get the amount of bytes....these equations i am presenting are all with the assumption that there is 512 bytes per sector.
this could be totally wrong, its just how i believe that it could be done.
or if you look at the ending sector of a drive you could subtract 1, divide by two and multiply by 512.
again these equations are something i am just throwing together by looking at numbers in front of me, they could be totally wrong or pretty accurate, i do not know, so i guess you can wait till someone else posts an answer...

The blocks/bytes ratio depends on how you've set up your filesystem at format time. Popular blocksizes are : 1024, 2048 and 4096 bytes. On the other hand low level utils like cpio assume a blocksize of 512 bytes, so maybe there are some historical anomalies that some guru can shed light on ?

To read raw blocks you could look into the dd util, or cpio in copy-pass mode.

I am reading from df command using 1024

well if you reading it using df then use df -h to get human readable numbers.

Yeah.....solaris system can't read df -h command. I believe some OS have blocks only...like VAX system.