A way to approximately compute that would be to use the 'sloccount' command
(in Trisquel repositories) to count the number of "source lines of code" in
both the source code of the vanilla Linux kernel and in that of Linux-libre.
Indeed, and as far as I understood, the blobs are dressed up as source code
(text files full of numbers, which hopefully span across many lines,
otherwise this method does not work). Alternatively, you can compare the size
(in bytes) of the binaries. On my 64 bit Trisquel 5.5 system:
$ sudo wc -c /boot/vmlinuz-3.0.0-24-generic
4670416 /boot/vmlinuz-3.0.0-24-generic
I guess the difference is very small. Anyway, you do not need many directives
to implement something nasty (a backdoor, a spyware, etc.). You want the
freedom to fix bugs in those blobs too (what is close to impossible because
they are blobs). That is why, if you value your own freedom, you would refuse
any proprietary piece of software.
