OSRS Combat Calc

OSRS Attack Accuracy Calculator

Calculate the chance that an ordinary melee accuracy roll succeeds. Compare accurate or controlled styles, offensive prayer and the defence of either a monster or a player without confusing Attack level with maximum damage.

Calculate your result

Adjust the fields to calculate your result.

Model limits: No special-attack accuracy, Void, Slayer effects, target debuffs, immunities or unusual weapon rolls. Player prayer and style controls are ignored for monsters. A successful accuracy roll is separate from the amount of damage that follows.

How OSRS Attack Accuracy Calculator Works

To use the OSRS Attack Accuracy Calculator, enter your Attack level, attack bonus, prayer and style, then the target’s Defence level and defence bonus, and read your hit chance.

  1. Enter your visible Attack level and the attack bonus for your attack type.
  2. Pick your Attack prayer and Attack style bonus.
  3. Pick the target type: monster or player.
  4. Enter the target’s Defence level and matching defence bonus.
  5. Pick the player’s Defence prayer and style, for player targets only.
  6. Read the hit chance, attack roll and defence roll.

OSRS Attack Accuracy Calculator Formula

The OSRS Attack Accuracy Calculator formula is Hit chance = 1 − (Defence roll + 2) ÷ (2 × (Attack roll + 1)) when the attack roll is higher.

Attack roll = (⌊Attack × prayer⌋ + style bonus + 8) × (attack bonus + 64)
Monster defence roll = (Defence + 9) × (defence bonus + 64)
Player defence roll = (⌊Defence × prayer⌋ + style bonus + 8) × (defence bonus + 64)
If Attack roll > Defence roll: hit chance = 1 − (Defence roll + 2) ÷ (2 × (Attack roll + 1))
Otherwise: hit chance = Attack roll ÷ (2 × (Defence roll + 1))

  • Accurate style adds 3 to effective Attack and controlled adds 1.
  • Piety multiplies Attack by 1.20 and Incredible Reflexes by 1.15.
  • Monsters add 9 to Defence and use no prayer or style.
  • Players add 8 plus their own Defence prayer and style bonus.

OSRS Attack Accuracy Calculator FAQ

How does accuracy work in OSRS?

Accuracy in OSRS works by comparing a random attack roll with a random defence roll; the attack hits when the attack roll is higher. Both rolls grow with level and with equipment bonus.

Does Attack level increase damage?

No, Attack level does not increase damage. Attack raises your attack roll, so more attacks land; Strength raises max hit.

What is a good hit chance in OSRS?

A hit chance above 70% is strong against most monsters. Heavily armoured bosses often keep melee accuracy between 30% and 50%.

Why does player defence use a different formula?

Player defence uses a different formula: players add 8, a Defence prayer and a Defence style bonus, while monsters add a flat 9.

Related calculators