In Europa Universalis II, unit weight is a number that abstractly quantifies how large a land military force is. The unit of measurement is called the army unit. Unit weights are positive integers.
Unit weight is computed from the military unit types composing a force, as follows:
- for infantry, 1000 men weigh 1 army unit
- for cavalry, 1000 men weigh 1 army unit
- for artillery, 10 guns weigh 1 army unit
The unit weights of all three types are computed separately, with each one rounded up to the next highest integer (rounding up is the "ceiling" operator). Then the three integers are added together; this is the force's unit weight.
For example, an army consists of 10500 infantry, 2000 cavalry, and 42 guns. Its unit weight is:
ceiling(10500/1000) + ceiling(2000/1000) + ceiling(42/10) = ceiling(10.5) + ceiling(2.0) + ceiling(4.2) = 11 + 2 + 5 = 18 army units
There are two circumstances where unit weight is computed in EU2. The forces weighed in the two cases are different:
- In determining land attrition, to determine the "crowding" in a province. In this case all armies of a country in the province are the force measured.
- In determining the size of passengers, whether they will fit in a particular fleet and how much space they take up if they do fit. In this case, each individual army is weighed separately.
As an example, a fleet with a passenger capacity of 11 units is carrying 8 tiny armies. They are weighed individually, then the weights are summed, so that they occupy 8 army units of passenger space. Three more army units of space are empty -- more passengers could be loaded. Now they unload into an empty province. In determining whether or not they suffer attrition, their sizes are added together before weighing; thus the total force present has just 8 cavalry, and has a unit weight of 1 army unit for computing attrition.