- 1 The hit chance formula
- 2 Calculating accuracy
- 3 Boss armour ratings
- 4 Update history
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[edit | edit source]
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 (as a percentage) is calculated as:
- is affinity
- is your accuracy
- is the target's armour rating. Generally, this is the sum of their armour and armour bonus granted by their Defence level.
Affinity[edit | edit source]
- 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[edit | edit source]
There is a single formula that relates level to accuracy bonus for base levels, weapons and monsters. Given a as the player's style-specific attack level (Attack for melee, Ranged and Magic for those respective styles), the formula is:
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:
|+ / /||126||2144|
|+ / /||128||2230|
|+ / /||130||2317|
|+ / /||132||2407|
|+ / / + / /||140||2795|
|+ / / + / /||142||2898|
Your base accuracy[edit | edit source]
Your accuracy is given by your style-specific attack level accuracy bonus added to your weapon's accuracy bonus. The style-specific level accuracy bonus is F(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.
Equipment penalty[edit | edit source]
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[edit | edit source]
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:
Hit chance boosts[edit | edit source]
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.
|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[edit | edit source]
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.
|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|
|(Illuminated) Bandos's Book of War||+3||12 seconds|
Hit Chance Examples[edit | edit source]
hit chance is capped at 100%, so all attacks will not miss.
Swapping for Dragonbane bolt will provide an additive bonus to hit chance:
and, therefore, reaching hit cap.
Boss armour ratings[edit | edit source]
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[edit | edit source]
God Wars Dungeon 2[edit | edit source]
The stats shown for Vindicta are for her second phase, which are higher than the first.
|Twin Furies (CM)||678||1486||2164|
Raids[edit | edit source]
Solo/Duo[edit | edit source]
|Queen Black Dragon||770||2074||2844|
Group[edit | edit source]
|Exiled Kalphite Queen||678||1694||2372|
|King Black Dragon||453||1132||1585|
Update history[edit | edit source]
- patch 1 September 2020 (Update):
- 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%
- Lowered the base hit-chance bonuses from some effects: