Hit chance

Hit chance is a calculated statistic that determines whether or not an attack will land. In its simplest form, hit chance is simply a function of accuracy, armour, and affinity; however, various modifiers (such as equipment or Buffs) can change hit chance.

When discussing changes to hit chance, modifiers are either additive (directly affecting hit chance) or multiplicative (affecting one of its variables). Additive bonuses are added directly the final calculation, whereas multiplicative bonuses modify a variable in the calculation. In this sense, accuracy is distinct from hit chance; the latter being a function of the former.

The hit chance formula

In combat, one's hit chance is the chance of successfully hitting a target (or the chance of a target hitting you), given your accuracy, the armour of your opponent, and the style you are using.

Your hit chance $H$ (as a percentage) is calculated as:

$H=Aff\times {\Bigg (}{\frac {a}{d}}{\Bigg )}$

Where:

• $Aff$ is affinity
• $a$ is your accuracy
• $d$ is the target's armour rating. Generally, this is the sum of their armour and armour bonus granted by their Defence level.

Affinity

Main article: Affinity

Monster affinity

In player-versus-monster combat, the monster generally has an affinity set for 3 or 4 types of attacks: melee, magic, ranged, and the specific weakness, if it has one. By default, those values are:

• 90 when using the target's specific weakness. (eg. slash, stab, arrows, bolts, air, fire, etc.)
• 65 when using a combat style the target is weak against, but not the specific weakness (eg. melee against a ranger)
• 55 when using a combat style the target is neutral against (eg. melee against a meleer)
• 45 when using a combat style the target is strong against (eg. melee against a mage)

Generic weaknesses to melee, ranged, or magic will use the respective melee, ranged, and magic affinity value rather than the weakness affinity value.

Some NPCs have custom set values for each affinity. For example, some bosses have 40 on all affinity values. Sometimes they may have no set weakness, but the affinities favour (or disfavour) one combat style anyway.

Player affinity

When the target is a player - be that in player-versus-player combat, or when calculating your defending chance in PvM - affinity is calculated a little differently. The neutral affinity is still 55, and up to 10 points are added or subtracted based on the armour the target is wearing for each of the three combat styles - players never have a specific weakness. The player's affinity is shown as Style bonus in the loadout interface; see Affinity#Player affinity and style bonus for details on calculating the actual affinity from style bonus.

Calculating accuracy

There is a single formula that relates level to accuracy bonus for base levels, weapons and monsters. Given a as the player's attack level, the formula is: $F(a)=0.0008a^{3}+4a+40$

For simplicity this formula will be referred to as F, so for example F(99) would be 1212.2, which rounds to the true value of 1212 (the level accuracy bonus of a player with level 99 Attack).

Note that drinking potions and using stat-boosting prayers will increase the input value for this. Assuming an attack/ranged/magic level of 99:

Effects	Lv	F
/ /	109	1512
	116	1753
	118	1826
+ / /	126	2144
+ / /	128	2230

Your base accuracy

$accuracy=F(a)+2.5\times F(weapon)$

Your accuracy is given by your Attack level accuracy bonus added to your weapon's accuracy bonus. The Attack level accuracy bonus is F(Attack level) and the weapon accuracy bonus is 2.5 * F(weapon tier), where F refers to the accuracy formula. Therefore, a player with 99 Attack using Drygore weaponry would have F(99) + 2.5 * F(90) = 3670 accuracy.

Weapon tier	2.5*F(tier)
70	1486
75	1694
80	1924
85	2178
90	2458
92	2577
99	3031

Equipment penalty

Wearing armour of the wrong class, excluding hybrid class, will negatively impact hit chance. Affected item slots include the helm, torso, legs, feet, hands, and off-hand slot. Depending on the weapon type, wearing armour from the class you are strong against (ie. if using Melee, this is Ranged) will result in an accuracy penalty that is 3/2 (x1.5) the item's armour stat. Wearing armour of the class you are weak against (if using Melee, this is Magic) will result in an accuracy penalty that is 4/5 (x0.8) of that item's armour stat. This penalty is designed to reinforce the combat triangle system and to prevent players from abusing the combat triangle weaknesses.

Accuracy boosts

There are various things that can be used to increase your accuracy rating; these simply multiply your accuracy value by a number, and these can be stacked with one another. These include:

Item	Multiplier	Percentage	Slot
Extreme dominion medallion	1.01	1%
Scrimshaw of Ranging / Magic / Attack	1.02	2%
Void knight armour	1.03	3%
Defenders / Reprisers / rebounders	1.03	3%
Brawler / Sharpshooter / Runic Accuracy	1.03	3%
Superior Scrimshaw of Ranging / Magic / Attack	1.04	4%
Blood / Shadow / Smoke / Ice Nihil (Familiars)	1.05	5%
Greater Brawler / Sharpshooter / Runic Accuracy	1.05	5%
Master Brawler / Sharpshooter / Runic Accuracy	1.07	7%
Supreme Brawler / Sharpshooter / Runic Accuracy / Berserker / Reckless / Maniacal	1.1	10%
Dragon Slayer Gloves (Dragons only, on Slayer task)	1.1	10%
Focus Sight / Hexcrest / Black mask Slayer helmet / Full slayer helmet (on Slayer task)	1.125	12.5%
Reinforced slayer helmet (on Slayer task)	1.13	13%
Strong slayer helmet (on Slayer task)	1.135	13.5%
Mighty slayer helmet (on Slayer task)	1.14	14%
Corrupted slayer helmet (on Slayer task)	1.145	14.5%
Salve amulet (Undead only)	1.15	15%
Salve amulet (e) (Undead only)	1.2	20%

Hit chance boosts

Also known as flat or additive accuracy bonuses. Unlike the above mentioned accuracy bonuses, these add the value directly to your final hit chance, rather than multiplying it. These can also be stacked with one another.

For example, a 10% hit chance bonus adds 10% to 60%, thus becoming 70% hit chance.

Item	Addition	Combat Style
Dragon battleaxe's special attack, Rampage	-10%	Melee
Keris (against Kalphites, also 33.3% damage boost and 2.5% chance to deal +200% damage instead +33.3%)	15%	Melee
Silverlight, Darklight, and Holy water (against certain demons, also a large damage boost)	20%	Melee
Keris with Desert amulet 3 or Desert amulet 4 worn (against Kalphites, also 33.3% damage boost and 5% chance to deal +200% damage instead of +33.3%)	25%	Melee
Darklight and Holy water (against certain demons; with the Darklight upgrade reward from Dimension of Disaster, also a large damage boost)	30%	Melee
Balmung (against Dagannoths, also 12.5% ability damage boost (7.5% against Dagannoth Supreme))	30%	Melee
Upgraded Balmung (against Dagannoths, also 22.5% ability damage boost (17.5% against Dagannoth Supreme))	45%	Melee
Dazing Shot and Greater Dazing Shot	-10% on your target's next attack	Ranged
Hexhunter bow (against magic-classed targets, also 12.5% damage boost)	10%	Ranged
Nightmare gauntlets	25% to Snipe, as well as allowing movement	Ranged
Bane ammo (against their attuned targets (Dragons, Abyssal, Basilisks, Wallasalkis), also 25% ability damage boost or 40% boost to auto-attacks)	30%	Ranged
Confuse	-5% for the affected target	Magic
Stagger	-10% for the affected target	Magic
Sonic Wave	6% on your next attack	Magic
Reaper necklace	0.1% per stack (3% max)	Any
Offensive Ultimate Abilities (Omnipower, Meteor Strike, Onslaught, etc)	25%	Any
Blisterwood weapons and Sunspear variants (against vampyres, vyrewatch, vyrelords/ladies, also chance to deal +100% damage)	50%	Any

Affinity modifiers

The following items and abilities increase the target's affinity, thereby making it easier to hit them. Only one of each can be active at once, and they stack additively with each other (i.e. using quake twice won't apply a +4 debuff, but quake with a barrelchest anchor special attack would be +6) up to a maximum of +10. Using the ability again refreshes the duration.

Effect	Debuff amount	Duration
Abilities
Quake	+2	1 minute
Special attacks
Guthix staff	+2	1 minute
Statius warhammer	+5	1 minute
Dragon hatchet	+3	1 minute
Barrelchest anchor	+4	1 minute
Bone dagger	+2	1 minute
Passives
(Illuminated) Bandos's Book of War	+3	12 seconds

Hit Chance Examples

Using Saradomin godsword (slash style) at Abyssal demon (slash weakness) with 99 attack:

• $Aff=90$
• $a=F(99)+2.5*F(75)=2906$
• $d=1486+F(70)=2080$
• $H=Aff\times a/d=90\times 2906/2080=125.7\%$

hit chance is capped at 100%, so all attacks will not miss.

On the other hand, using Sunspear (ranged) with 99 ranged in void knight armour will result in misses:

• $Aff=45$
• $a=F(99)+2.5*F(78)=3041$
• $d=1486+F(70)=2080$
• $H=mod\times Aff\times a/d=1.03\times 45\times 3041/2080=67.8\%$

For a Queen Black Dragon bossing situation, using Royal crossbow, Overload, Anguish, and Royal bolts with 99 ranged will result in misses:

• $Aff=50$
• $a=F(126)+2.5*F(80)=4068$
• $d=1924+F(80)=2693$
• $H=Aff\times a/d=50\times 4068/2693=75.5\%$

Swapping for Dragonbane bolt will provide an additive bonus to hit chance:

• $H_{dbane}=H+mod=0.755+0.3=105.5\%$

and, therefore, reaching hit cap.

Boss armour ratings

The tables below are for quick look-up of the total armour rating of current bosses. For the affinity values to your combat style, refer to the boss's individual page. HM and CM refers to hard mode and challenge mode, respectively.

God Wars Dungeon 1

Bosses include: Commander Zilyana, General Graardor, Kree'arra, K'ril Tsutsaroth, and Nex.

Boss	F()	Armour	Total
Normal Mode	678	1299	1977
Hard Mode	678	1694	2372
Nex	770	1924	2694
Nex (Aod)	871	2765	3636

God Wars Dungeon 2

The stats shown for Vindicta are for her second phase, which are higher than the first.

Boss	F()	Armour	Total
Gregorovic	678	1694	2372
Gregorovic (CM)	770	1924	2694
Helwyr	594	1486	2080
Helwyr (CM)	678	1694	2372
Twin Furies	594	1486	2080
Twin Furies (CM)	678	1486	2164
Vindicta	770	1924	2694
Telos	770	1924	2694

Raids

Boss	F()	Armour	Total
Beastmaster Durzag	1106	2765	3871
Yakamaru	1212	3031	4243

Solo/Duo

Boss	F()	Armour	Total
The Magister	1031	2577	3608
Araxxor	871	2458	3329
Araxxi	770	1924	2694
Har-Aken	770	1924	2694
Queen Black Dragon	770	2074	2844

Group

Boss	F()	Armour	Total
Chaos Elemental	579	1447	2026
Corporeal Beast	678	1694	2372
Giant mole	293	732	1025
Dagannoth Kings	564	1409	1973
Kalphite King	871	2178	3049
Kalphite Queen	594	1486	2080
Exiled Kalphite Queen	678	1694	2372
King Black Dragon	453	1132	1585
Vorago	983	2178	3161

Update history

The update history project is a work-in-progress – not all updates to this topic may be covered below. See here for how to help out!

• patch 12 September 2016 (Update):
  • Lowered the base hit-chance bonuses from some effects:
    • Statius's Warhammer special attack, 10% -> 5%
    • Dragon hatchet special attack, 5% to 3%
    • Barrelchest anchor special attack, 5% to 4%
    • Bone dagger special attack, 5% to 2%
    • Bandos'/Illuminated book of war random effect, 5% to 3%

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