Combat Level
The first formula is used to calculate your Base Combat Level.
[math]\displaystyle{ \text{Base Combat Level} = 0.25 * (\text{Defence Skill Level} + \text{Hitpoints Skill Level} + (\text{Prayer Skill Level} / 2) }[/math]
The second set of formulas calculates your Offensive Combat Levels, only the highest result is used.
[math]\displaystyle{ \text{Melee Combat Level} = 0.325 * (\text{Attack Skill Level} + \text{Strength Skill Level}) }[/math]
[math]\displaystyle{ \text{Ranged Combat Level} = 0.325 * (3 * \text{Ranged Skill Level} / 2) }[/math]
[math]\displaystyle{ \text{Magic Combat Level} = 0.325 * (3 * \text{Magic Skill Level} / 2) }[/math]
The third formula is used to calculate your Combat Level, rounded down to the nearest whole number.
[math]\displaystyle{ \text{Combat Level} = \text{Base Combat Level} + \text{Highest Offensive Combat Level} }[/math]
Melee Accuracy Rating
The first formula is used to calculate your Effective Melee Attack Level. The Attack Style Bonus for melee is 1.
[math]\displaystyle{ \text{Effective Melee Attack Level}=\text{Attack Skill Level} + 8 + \text{Attack Style Bonus} }[/math]
The second formula is used to calculate your Melee Accuracy Rating. Your Melee Attack Bonus can be found in your Equipment Stats and changes depending on the Attack Style selected. Simply substitute your Stab Bonus, Slash Bonus, or Defend Bonus, with Melee Attack Bonus in this formula. The potion and prayer bonuses, will be the relevant numbers written in the potion and prayer descriptions.
[math]\displaystyle{ \text{Melee Accuracy Rating} = \text{Effective Melee Attack Level} * (\text{Melee Attack Bonus} +64) * (1 + \text{Potion Accuracy Rating Bonus} / 100) * (1 + \text{Prayer Accuracy Rating Bonus} / 100) }[/math]
Ranged Accuracy Rating
The first formula is used to calculate your Effective Ranged Attack Level. The Attack Style Bonus when using the Accurate Attack Style is 4, otherwise it's 1.
[math]\displaystyle{ \text{Effective Ranged Attack Level}=\text{Attack Skill Level} + 8 + \text{Attack Style Bonus} }[/math]
The second formula is used to calculate your Ranged Accuracy Rating. Your Ranged Attack Bonus can be found in your Equipment Stats, under Offensive Stats with the bow and arrow icon. The potion and prayer bonuses, will be the relevant numbers written in the potion and prayer descriptions.
[math]\displaystyle{ \text{Ranged Accuracy Rating} = \text{Effective Ranged Attack Level} * (\text{Ranged Attack Bonus} +64) * (1 + \text{Potion Accuracy Rating Bonus} / 100) * (1 + \text{Prayer Accuracy Rating Bonus} / 100) }[/math]
Magic Accuracy Rating
The first formula is used to calculate your Effective Magic Attack Level. The Attack Style Bonus for magic is 1.
[math]\displaystyle{ \text{Effective Magic Attack Level}=\text{Attack Skill Level} + 8 + \text{Attack Style Bonus} }[/math]
The second formula is used to calculate your Magic Accuracy Rating. Your Magic Attack Bonus can be found in your Equipment Stats, under Offensive Stats with the wizard hat icon. The potion and prayer bonuses, will be the relevant numbers written in the potion and prayer descriptions.
[math]\displaystyle{ \text{Magic Accuracy Rating} = \text{Effective Magic Attack Level} * (\text{Magic Attack Bonus} +64) * (1 + \text{Potion Accuracy Rating Bonus} / 100) * (1 + \text{Prayer Accuracy Rating Bonus} / 100) }[/math]
Chance to Hit
To calculate the chance an attack will hit, the Accuracy Rating of the attacker is compared to the relevant Evasion Rating of the defender. If the attacker's Accuracy Rating is lower than the defender's evasion rating the formula looks like this.
[math]\displaystyle{ \text{Hit Percent Chance}=\ (0.5 * \text{Accuracy Rating} / \text{Evasion Rating}) * 100 }[/math]
If the attacker's Accuracy Rating is higher than the defender's Evasion Rating the formula looks like this.
[math]\displaystyle{ \text{Hit Percent Chance}=\ (1 - 0.5 * \text{Evasion Rating} / \text{Accuracy Rating}) * 100 }[/math]
When your Accuracy Rating and the target's Evasion Rating are the same, the chance to hit is 50%. The higher your Accuracy Rating is above the targets Evasion Rating, the less valuable each point will be. At double you your targets Evasion Rating, you will hit 75% of the time, at triple, you will hit 83.3% of the time.
Max Hit
The first formula is used to calculate your Effective Strength Level.
[math]\displaystyle{ \text{Effective Strength Level = Strength Skill Level + 8 + 1} }[/math]
The second formula is used to calculate your Max Hit. Your Strength Bonus can be found in your Equipment Stats. The potion and prayer bonuses, will be the relevant numbers written in the potion and prayer descriptions.
[math]\displaystyle{ \text{Max Hit} = 10 * ((1.3 + \text{Effective Strength Level} / 10 + \text{Strength Bonus} / 80 + \text{Effective Strength Level} * \text{Strength Bonus} / 640) * (1 + \text{Potion Strength Bonus} / 100) * (1 + \text{Prayer Strength Bonus} / 100)) }[/math]
Magic Max Hit
Your Max Hit with spells changes depending on the spell being used. Spell Max Hit is in the spells description. Your Magic Damage Bonus can be found in your Equipment Stats under % Damage Bonus. The potion and prayer bonuses, will be the relevant numbers written in the potion and prayer descriptions.
[math]\displaystyle{ \text{Magic Max Hit} = \text{Spell Max Hit} * (1 + \text{Magic Damage Bonus} / 100) * (1 + \text{Prayer Magic Damage Bonus} / 100) * (1 + \text{Potion Magic Damage Bonus}) }[/math]
Melee Evasion Rating
The first formula is used to calculate your Effective Defence Level. Your Defence Style Bonus is 1. When using the Longranged Attack Style your Defence Style Bonus is 3.
[math]\displaystyle{ \text{Effective Defence Level} = \text{Defence Skill Level} + 8 + \text{Defence Style Bonus} }[/math]
The second formula is used to calculate your Melee Evasion Rating. Your Melee Defence Bonus can be found in your Equipment Stats under Defensive Stats with a shield icon. The potion and prayer bonuses, will be the relevant numbers written in the potion and prayer descriptions.
[math]\displaystyle{ \text{Evasion Rating} = \text{Effective Defence Level} * (\text{Melee Defence Bonus} + 64) * (1 + \text{Potion Evasion Rating Bonus} / 100) * (1 + \text{Prayer Evasion Rating Bonus} / 100) }[/math]
Ranged Evasion Rating
The first formula is used to calculate your Effective Defence Level. Your Ranged Defence Style Bonus is 1.
[math]\displaystyle{ \text{Effective Defence Level} = \text{Defence Skill Level} + 8 + \text{Ranged Defence Style Bonus} }[/math]
The second formula is used to calculate your Ranged Evasion Rating. Your Ranged Defence Bonus can be found in your Equipment Stats under Defensive Stats with a bow and arrow icon. The potion and prayer bonuses, will be the relevant numbers written in the potion and prayer descriptions.
[math]\displaystyle{ \text{Ranged Evasion Rating} = \text{Effective Defence Level} * (\text{Ranged Defence Bonus} + 64) * (1 + \text{Potion Evasion Rating Bonus} / 100) * (1 + \text{Prayer Evasion Rating Bonus} / 100) }[/math]
Magic Evasion Rating
The first formula is used to calculate your Effective Magic Defence Level. The result here is always rounded down to the nearest whole number.
[math]\displaystyle{ \text{Effective Magic Defence Level} = \text{Magic Skill Level} * 0.7 + \text{Defence Skill Level} * 0.3 }[/math]
The second formula is used to calculate your Magic Evasion Rating. Your Magic Defence Bonus can be found in your Equipment Stats under Defensive Stats with a wizard hat icon. The potion and prayer bonuses, will be the relevant numbers written in the potion and prayer descriptions.
[math]\displaystyle{ \text{Magic Evasion Rating} = \text{Effective Magic Defence Level} * (\text{Magic Defence Bonus} + 64) * (1 + \text{Potion Evasion Rating Bonus} / 100) * (1 + \text{Prayer Evasion Rating Bonus} / 100) + 8 + 1) }[/math]