As vtsao just said (thanks, Vincent), BBB recommended base size is 1" square; infantry units normally between 3 and 7 bases strong; cavalry rarely more than 2 or 3 bases; artillery single-base units.
Troop scale varies per scenario. Typically 1,000-2,000 men or 24-48 guns per base; can go up to 3,000+ for the biggest battles, or down to 500 or fewer for smaller ones. Ground scale and time scale vary as well to keep things in proportion and fit battles on the table.
Inkerman scale is 666 men or 16 guns per base. About 40 bases on the Allied side, 50-60+ Russians (depending on reinforcement choices). It plays out as a thin red (and blue) line trying to avoid being overrun or swarmed past by masses of Russians.
Chris