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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

is affinity $ a $ is your accuracy

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

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

Item Lv 2.5*F(Lv) 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:

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.

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 +5) up to a maximum of +10. Using the ability again refreshes the duration.

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=1608+F(70)=2202 $

$ H=Aff \times a/d=118.8% $

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=1608+F(70)=2202 $

$ H=1.03 \times Aff \times a/d=64.0% $

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=2075+F(80)=2845 $

$ H=Aff \times a/d=71.5% $

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

$ H=Aff \times a/d + 30=101.5% $

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