ok so I've gotten myself involved in vs debate with some friends pitting the 40k imperium vs Starwars empire

the main person I'm arguing against says that star wars outnumbers 40k so much that even 10k battle ships wont win it, his figure was 25,000 star destroyers.
I myself was interested to find out just how many ships the imperium did have, after all it is fighting everyone else in 40k so 25000 ships seems to small a figure

So armed with the Battle fleet Gothic rule book I got to work
this is what i figured out
from battle fleet gothic rule book page 88
normal battle fleet is 50-75 ships also lots of non warp capable in adition to this
from page 88 of the BFG
The Imperium is divided into sectors
1 battle fleet per sector
there is 50 to 75 ships in a normal Battle fleet
a sector is 8,000,000 cubic lightyears
39 million million (3.9x10^13) cubic light years is volume of milky way