Hi!
On BOA1 the losses are somewhat abstracted in "Hits".
On the newer games (AACW, NCP, WIA) actual numbers of men/guns and horses losses were introduced.
To understand how bad your losses were, take a look at the unit detail panel.
There, clicking on each sub element you will see how many hits it haves (IIRC about 8-10 per standard infantry element). So... if a unit (regiment) has 4 elements, it has around 40 hits.
A 10 regiment stack (400 hits) that losses 200 hit in battle has suffered a 50% casualties
Regarding men, well, you can do the maths... if let say a regiment has 1000 men, each hit represent... 50 or so.
If you buy WIA, you will have all this maths done for you by the game
