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 modifiers apply.

Solder Stats

A typical XCOM rookie starts off with a flat 65 Aim stat. As their rank improves, they gain additional points at a static rate. Second Wave options can instead be used to mix up the abilities of your ranks - "Not Created Equally" has them start with an aim stat of somewhere from 55 to 80, whereas "Hidden Potential" randomises gains.

In addition to their base stats, each class gains access to a selection of perks which can either improve accuracy, decrease it in exchange for another bonus, or decrease that of the anyone firing at them (by way of adding defense):

Assaults

The Assault class sports moderate accuracy, but their shotguns grant huge bonuses at near range - and they're very good at closing the distance between their targets. At distances further then ten tiles, their pistols (or perhaps rifles, if equipped) make for more reliable damage, albeit somewhat reduced in power. They can acquire abilities that reduce enemy accuracy when up in the alien's faces.

Squaddie	Corporal	Sergeant	Lieutenant	Captain	Major	Colonel	Total Gains
70 (+5)	73 (+3)	76 (+3)	79 (+3)	82 (+3)	85 (+3)	89 (+4)	+ 24

Aim-related abilities:

• Flush: Reduced damage for a +??? aim (also forces the target to move).
• Rapid Fire: Two shots, but at a -15 penalty to each.
• Tactical Sense: Enemy units that can see the assault take a penalty of five times the total number of such units (up to -20).

Heavys

Heavies have very poor aim compared to other classes, but make up for it with a number of abilities which ignore the stat, and at close range their shots are still fairly reliable. Their rockets always have at least a 90% chance to strike their targets, and having them open up on your enemies first can often result in them destroying alien cover or granting other accuracy benefits to their squad-mates (whether the heavies themselves manage to hit or not).

Squaddie	Corporal	Sergeant	Lieutenant	Captain	Major	Colonel	Total Gains
67 (+2)	68 (+1)	69 (+1)	70 (+1)	71 (+1)	73 (+2)	75 (+2)	+10

Aim-related abilities:

• Holo-Targeting: +10 to all other allied fire on the target until next turn.
• Suppression: -30 to target's aim until next turn.

Snipers

Snipers gain no accuracy bonuses from their high-powered rifles, and in fact take a penalty if they try to use them at close range (pistols have a better chance to hit at distances less then ten tiles). However, their innate accuracy stats are through the roof, and higher ranks give them optional abilities that push them ever higher.

Squaddie	Corporal	Sergeant	Lieutenant	Captain	Major	Colonel	Total Gains
75 (+10)	78 (+3)	81 (+3)	84 (+3)	88 (+4)	95 (+7)	105 (+10)	+ 40

Aim-related abilities:

• Damn Good Ground: A passive +10 aim (and a -10 penalty to any shots fired back) while above the target.
• Executioner: A passive +10 aim if the target has less then 50% health.
• Opportunist: Removes the aim penalty (and crit restriction) from Overwatch shots.
• Snap Shot: Allows firing as a second action, but at a -20 penalty. (Due to a bug, taking this perk applies this penalty to extra shots granted by Double Tap as well.)
• Disabling Shot: Shot empties the target's weapon, but at a -10 penalty.
• Low Profile: -20 penalty to units firing on the sniper if in low cover.

Supports

Supports are very "mid-range" in terms of accuracy, though their damage output isn't anything to brag about. It should be noted that regardless of range, their rifles and pistols will always have the same chance to hit (excluding any weapon-specific bonuses, such as that available to the Light Plasma Rifle or Foundry-upgraded pistols). Their smoke grenades can inflict accuracy penalties against units firing at those the supports aim to protect.

Squaddie	Corporal	Sergeant	Lieutenant	Captain	Major	Colonel	Total Gains
70 (+5)	73 (+3)	76 (+3)	79 (+3)	82 (+3)	85 (+3)	90 (+5)	+ 25

Aim-related abilities:

• Combat Drugs: +20 bonus to units firing from within the support's smoke clouds.
• Smoke Grenade: -20 penalty to anyone firing at units in the cloud.
• Rifle Suppression: -30 to target's aim until next turn.
• Dense Smoke: An additional -20 penalty to units firing into the support's smoke clouds.

Alien Stats

Aliens are, for the most part, about on par with lower-ranked XCOM soldiers, though on difficulty levels above normal they receive a +10 aim/crit bonus (and an extra +10 aim for Outsiders and Muton Elites on Impossible).

It's worth noting that the Light Plasma Rifle seen earlier on in the game (especially favoured by Thin Men) confers an additional +10 bonus to its wielder. Those aliens which use melee attacks (the Chryssalid, the Zombie, and the Muton Berserker) never miss.

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

Weapon Range

An aim bonus may be granted based on the distance to the target, depending on the type of weapon used. For the purposes of determining this bonus, 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, each'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 (ten tiles or more), then there's no penalty.

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 (again, a distance of ten tiles or more is where range 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 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.