In combat, ability damage is a number based on your skills, weapons, and armour, which is used by almost all abilities to determine how strongly they can hit. Ability damage is affected by damage-boosting items. It is closely related to the auto-attack damage shown in the combat interface, but it varies in notable and significant ways.

Ability damage can be viewed in the abilities tab of offensive stats, under the loadout tab of the worn equipment interface.

Abilities use the player's ability damage to determine their maximum hit. In general, the damage is multiplied by a particular number that is stated on the interface (for example, Slice's maximum hit is $ 120A $). A normal ability hit will deal between 20% to 100% of its maximum damage. If the ability deals between 95% to 100% of its maximum damage, it is a critical hit.

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Calculating ability damage

Magic

For magic, your ability damage $ D $ is:

$ D = \begin{cases} 2.5 M + \min(9.6 t_m,s_m) + b & \text{for main-hand}\\ 1.25 M + \min(4.8 t_o,s_o) + 0.5b & \text{for off-hand}\\ 3.75 M + \min(14.4 t_m,s_m) + 1.5b & \text{for two-hand}\\ \end{cases} $

Where:

$ M $ is your level in Magic, including boosts

is your level in Magic, including boosts $ t_m $ is the tier of your main-hand weapon

is the tier of your main-hand weapon $ t_o $ is the tier of your off-hand weapon

is the tier of your off-hand weapon $ s_m $ is the damage of your main-hand spell

is the damage of your main-hand spell $ s_o $ is the damage of your off-hand spell

is the damage of your off-hand spell $ b $ is the sum of all Magic bonuses from armour and jewellery.

Main- and off-hand spell damage can be found by mousing over the damage value in Offensive Stats. For spell damage with a staff, take it instead as 1.5 times the spell damage from a wand of equal level.

Decimal results are rounded down. When dual-wielding, the results for main- and off-hand ability damage are to be added together.

Melee

For melee, your ability damage $ D $ is

$ D = \begin{cases} 2.5 S + d_m \times s_m + b & \text{for main-hand}\\ 1.25 S + d_o \times s_o + 0.5b & \text{for off-hand}\\ 3.75 S + d_m \times s_m + 1.5b & \text{for two-hand}\\ \end{cases} $

Where:

$ S $ is your level in Strength, including boosts

is your level in Strength, including boosts $ d_m $ is the damage of your main-hand weapon

is the damage of your main-hand weapon $ d_{o} $ is the damage of your off-hand weapon

is the damage of your off-hand weapon $ s_m $ and $ s_o $ are multipliers, based on the speed of your main- and off-hand weapons, that serve to localise weapon damage: $ s = \begin{cases} \frac{96}{149} \approx 0.644295 & \text{Average}\\ \frac{192}{245} \approx 0.783673 & \text{Fast}\\ 1 & \text{Fastest}\\ \end{cases} $

and are multipliers, based on the speed of your main- and off-hand weapons, that serve to localise weapon damage: $ b $ is the sum of all Strength bonuses from armour and jewellery.

Decimal results are rounded down. When dual-wielding, the results for main- and off-hand ability damage are to be added together.

Ranged

For ranged, your ability damage $ D $ is:

$ D = \begin{cases} 2.5 R + \min(9.6 t_m,d_a) + b & \text{for main-hand}\\ 1.25 R + \min(4.8 t_o,0.5d_a) + 0.5b & \text{for off-hand}\\ 3.75 R + \min(14.4 t_m,1.5d_a) + 1.5b & \text{for two-hand}\\ \end{cases} $

Where:

$ R $ is your level in Ranged, including boosts

is your level in Ranged, including boosts $ t_m $ is the tier of your main-hand weapon

is the tier of your main-hand weapon $ t_o $ is the tier of your off-hand weapon

is the tier of your off-hand weapon $ d_a $ is the damage of your ammunition

is the damage of your ammunition $ b $ is the sum of all Ranged bonuses from armour and jewellery.

Shieldbows count as main-handed for the calculation. If using throwing weapons or a bow that generates its own arrows, ability damage is calculated in the same fashion as with melee weapons.

Decimal results are rounded down. When dual-wielding, the results for main- and off-hand ability damage are to be added together.

Boosting ability damage

Prayer

Prayers increase your ability damage by a set percentage, which can be found on the Prayer page. Prayers do not affect the damage of bleed abilities.

Potions

The effect of potions is twofold.

Potions increase your visible Magic, Strength and Ranged levels, which are used during the ability damage calculation.

Each boosted level provides $ (4 - 8) $ extra damage to each hit you deal. Precise, Equilibrium, and Biting perks affect this extra damage. (With Precise 4 and Equilibrium 2, this becomes $ (4.69 - 7.93) $ extra damage.) This extra damage is not affected by prayer multipliers but is affected by all other multipliers. This extra damage has no effect on bleed abilities.

Other boosts

There are many miscellaneous items and situations that can boost your ability damage. If multiple percentage multipliers stack, they will stack in a multiplicative fashion. All of them work on bleeds except for Void Knight equipment and the slayer helmet and equivalents.