How is max hit calculated in OSRS?

Effective strength = floor((Strength + boost) * prayer) + style bonus + 8. Max hit = floor(0.5 + effectiveStr * (strengthBonus + 64) / 640). The strength bonus comes from your equipped gear.

How is hit chance worked out?

Both sides compute an attack/defence roll. Attack roll = effectiveAttack * (equipAttackBonus + 64). Defence roll = effectiveDefence * (equipDefenceBonus + 64). If attack roll > defence roll, accuracy = 1 - (defRoll + 2) / (2*(attRoll + 1)); otherwise accuracy = attRoll / (2*(defRoll + 1)).

What is the +8 in the effective level?

OSRS adds a flat +8 to effective attack and strength levels after applying prayer and style bonuses. It is a baseline constant in the combat formula that applies to every player.

How does attack style affect damage?

Aggressive style adds +3 to effective strength (more max hit), Accurate adds +3 to effective attack (more accuracy), Controlled adds +1 to both, and Defensive adds +3 to defence. The right style depends on whether you are accuracy- or damage-capped.

How is DPS derived from hit chance and max hit?

Average damage per attack = hitChance * (maxHit / 2), since a successful hit rolls uniformly from 0 to max. DPS = averageDamage / (attackSpeed * 0.6), because each weapon speed tick is 0.6 seconds.

Old School RuneScape DPS Calculator

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The Old School RuneScape DPS Calculator implements the game’s real melee combat formula — effective levels, the attack/defence roll comparison, max hit, and the 0.6-second tick speed — so you can compare gear and styles with accurate numbers instead of guesses.

How it works

Effective levels. Apply the prayer multiplier, then the style bonus, then add 8:

effStr = floor( (StrengthLvl + boost) * prayerStr ) + styleStr + 8
effAtt = floor( (AttackLvl + boost) * prayerAtt ) + styleAtt + 8

Max hit from effective strength and the gear strength bonus:

maxHit = floor( 0.5 + effStr * (strengthBonus + 64) / 640 )

Hit chance compares an attack roll against a defence roll:

attRoll = effAtt * (equipAttackBonus + 64)
defRoll = effDef * (targetDefenceBonus + 64)

if attRoll > defRoll:  acc = 1 - (defRoll + 2) / (2 * (attRoll + 1))
else:                  acc = attRoll / (2 * (defRoll + 1))

DPS. A landed hit rolls uniformly from 0 to max, so the average per attack is acc * maxHit / 2. Each weapon attack-speed tick is 0.6 seconds, so:

DPS = (acc * maxHit / 2) / (attackSpeed * 0.6)

Example

A scimitar (speed 4) with 70 Strength, an aggressive style, and a +68 strength bonus gives an effective strength of 70 + 3 + 8 = 81 and a max hit of floor(0.5 + 81 * (68 + 64) / 640) = 16. Pair that with the accuracy roll against your target’s defence to read DPS instantly.