How can I figure out the size of a block on a busybox device?

This is the output of df on my little embedded device:

# df
Filesystem           1k-blocks      Used Available Use% Mounted on
rootfs                    3008      3008         0 100% /
/dev/root                 3008      3008         0 100% /
/dev/mtdblock6            3072      2528       544  82% /system
/dev/mtdblock7             512       248       264  48% /param

And I'm trying to figure out exactly how much a block is and how much free memory I have. The common way to find the size of a block appears to be:

blockdev --getbsz partition

but this is a tiny ucLinux/Busybox device and doesn't have blockdev and a lot of other tools.

How can I figure out the size of my blocks?