OSRS Combat Calc

OSRS Magic Accuracy Calculator

Compare your magic attack roll against a monster’s magic defence roll. Add your prayer, magic attack bonus and damage bonus to see hit chance, spell max hit and damage per second.

Calculate your result

Adjust the fields to calculate your result.

Model limits: Uses the standard NPC magic defence roll. Player targets, powered-staff max hit scaling, Tumeken’s shadow, elemental weaknesses, Smoke and Ice effects and special spell mechanics are not modelled. Enter the spell’s base max hit for your Magic level.

How OSRS Magic Accuracy Calculator Works

To use the OSRS Magic Accuracy Calculator, enter your Magic level, prayer, gear and the monster’s magic defence, then read your hit chance, max hit and damage per second (DPS).

  1. Enter your visible Magic level, including boosts.
  2. Pick your Magic prayer, powered staff style and Void Magic.
  3. Enter your magic attack bonus and pick a Slayer helmet or salve amulet boost.
  4. Enter the monster’s Magic level and magic defence bonus.
  5. Enter the spell’s base max hit, your magic damage bonus and casting speed.

OSRS Magic Accuracy Calculator Formula

The OSRS Magic Accuracy Calculator formula is Magic attack roll = Effective Magic × (magic attack bonus + 64), compared with the monster’s magic defence roll.

Effective Magic = ⌊Magic level × prayer⌋ (× 1.45 with Void) + 2 (accurate powered staff) + 9
Attack roll = ⌊Effective Magic × (magic attack bonus + 64) × target boost⌋
Monster defence roll = (monster Magic level + 9) × (magic defence bonus + 64)
Max hit = ⌊base spell max hit × (1 + magic damage % ÷ 100)⌋

  • Augury multiplies Magic by 1.25 and Mystic Might by 1.15.
  • A Slayer helmet (i) on task or salve amulet (ei) against undead multiplies the attack roll by 1.15.
  • Monsters defend against Magic with their Magic level, not their Defence level.

OSRS Magic Accuracy Calculator FAQ

How does magic accuracy work in OSRS?

Magic accuracy works by comparing your magic attack roll with the monster’s magic defence roll. Monsters defend with their Magic level and magic defence bonus.

Why do monsters use Magic level to defend against spells?

Monsters use Magic level: Old School RuneScape (OSRS) rolls an NPC’s magic defence from its Magic level, not its Defence level. Low-Magic monsters are easy targets for spells.

How much does Augury add to magic accuracy?

Augury adds 25% to effective Magic for accuracy.

How is spell max hit calculated?

Spell max hit is calculated as the spell’s base max hit × (1 + magic damage % ÷ 100), rounded down.

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