Chance to Hit (EU2012)

Attack (or Aim) is the statistic used to calculate the chance of hitting a given target (somewhat akin to the original game's Firing Accuracy). Its value can be raised with the use of selected weapons, equipment and/or class abilities; or lowered by the target's use of cover or as a result of other penalties.

The final "chance to hit" is taken by simply adding all bonuses / penalties together. Just before ok'ing a shot on your target, you may select "More Info" within the game's HUD to see a list of which apply to the shot you're about to take.

Solder Stats

A typical XCOM rookie starts off with a flat 65 Aim stat (or between 55 to 80 with Second Wave's unlockable "Not Created Equally" option enabled). As their rank improves, they gain additional points:

Class	Squaddie	Corporal	Sergeant	Lieutenant	Captain	Major	Colonel	Total
Assault	+ 5	+ 3	+ 3	+ 3	+ 3	+ 3	+ 4	+ 24
Heavy	+ 2	+ 1	+ 1	+ 1	+ 1	+ 2	+ 2	+ 10
Sniper	+ 10	+ 3	+ 3	+ 3	+ 4	+ 7	+ 10	+ 40
Support	+ 5	+ 3	+ 3	+ 3	+ 3	+ 3	+ 5	+ 25

Second Wave's "Hidden Potential" option can instead be used to randomise gains.

Alien Stats

Name	Aim	Name	Aim
Sectoid	65	Outsider	70
Thin Man	65	Floater	50
Chryssalid	Melee	Zombie	Melee
Muton	70	Drone	60
Cyberdisc	70	Sectoid Commander	85
Muton Berserker	Melee	Sectopod	80
Heavy Floater	70	Muton Elite	80

Melee attacks always hit. On the Classic and Impossible difficulty levels, aliens receive a +10 aim/crit bonus (and an extra +10 aim for Outsiders and Muton Elites on Impossible).

Weapon Range

An aim bonus may be granted based on the distance to the target, depending on the type of weapon used. Of all those available in the game, guns always fall into one of three different categories: shotguns, sniper rifles, and "everything else".

Most - from the humble Pistol through to the legendary Heavy Plasma - are treated the same in terms of accuracy. Have two soldiers at the same distance from your target, they'll get the same range bonus as the other. Such weapons may only receive range bonuses - if you're too far away to receive one, then there's no penalty, though depending on how far out of range you are you may need to move forward multiple tiles before you start noticing an improvement of your aim (the maximum distance before the range bonus is ignored is nine titles).

The rifles used by Snipers, on the other hand, are the reverse: being closer to your target inflicts a penalty, and moving further away simply lessons this (until past the same nine tile mark, where range again ceases to have any bearing on accuracy).

The only weapon type that has access to a range bonus in addition to a penalty is the shotgun class used by Assaults. A distance of less then ten tiles sees their accuracy spike up at a much faster rate then other weapons; but a distance further then ten tiles inflicts a penalty at the exact same rate (though oddly enough, no such penalty applies to their damage - if they happen to hit at range, they'll be just as devastating as a point-blank blast to the face).

The following formulas describe accuracy drop-off. Again, note that if the standard weapon bonus drops below 0, it's ignored, if the sniper bonus rises above 0 it's ignored, and the shotgun formula always applies. x and y describe the distance in tiles along each axis between the target and the shooter (i.e. Pythagoras is used to get the proper distance on any angle). Final results are rounded down.

Standard Guns	Shotgun Class	Sniper Class

In addition, a very slight fractional penalty may be applied depending on the direction the shot is coming from. For example, a soldier with a rifle sitting an exact two tiles away from an alien may have a 33% range bonus, but another soldier with the same weapon and at the same distance might only get a 32% bonus if he's on a 90° angle (it appears this is because the base bonus drops from 42 to 41.6 in such a case).

Note: The partial brackets used in the shotgun formula represent a floor operation, or to put it another way, "round this value down".

Note 2: These formulas may not be 100% accurate.

More Stuff To Put On This Page

Need tables listing the different bonuses/penalties available to each soldier class, equipment bonuses (including foundry upgrades (and notes about the bugs involved with those)), environmental factors (such as cover, stat damage, overwatch, height), and innate armour/alien defence bonuses.

Critical hits would also be best explained on this page - though they're more to do with damage, this is probably where people will look for information about them, and the mechanics used to tally up chance-to-crit are about the same as chance-to-hit.