# What is the calculation behind Attack, Defense and Spellpower?

Could someone please explain how Attack and Defence affect Monster Stats and how Spellpower affects Spells?

Every creature has a base Attack / Defense score.

When combat starts, your creatures get a bonus to Attack / Defense equal to your Hero's Attack / Defense scores.

If a creature's combined attack is greater than their target's defense, they take an additional 5% damage per point of difference, up to a cap of +300% damage (when attack is 60 greater than defense)

Conversely, if a creature's combined attack is less than their target's defense, they deal 2.5% less damage, down to 70% (when defense is 12 greater than attack).

Spellpower's exact effect varies depending on the spell. For instance, Magic Arrow does (10 * spell power) + 10 damage.

Haste has a constant effect and lasts Spell Power turns in duration.

• Great answer for such an old game like this. (+1) Could you provide a source please? Commented Apr 23, 2013 at 18:55
• Commented Apr 23, 2013 at 21:19
• What about the secondary skill modifiers and archery calculation? Commented Jun 7, 2014 at 8:36

About defense reduction in accepted answer: 70% is delta (coefficient 0.3), so defense-attack limit is 28 (not 12). If hero has offense / armor - it becomes more complicated: coefficients 1.1/1.2/1.3 for offender-damage (direct melee, not retaliation) and 0.95/0.90/0.85 armourer-received-damage (for basic/advanced/expert level).

For precise formula one sould also count offense/armor specialists (crack,gundula / tazar,neela,mephala). Same for archery, ballista, spells, specialists for them (and for creatures: galthran/shakti etc.), creature capabilities (there is champion's bonus, but not vs alebards; angels produce 50% more damage against devils etc.).

Unfortunatly on mightandmagic.wikia.com formula is incorrect (e.g. attack/deffense should be separated), more correct manual on russian-funsite: section "combat", search by "D(bas)" (maybe google-traslate could give comprehensable result).

Since game is somewhat popular there is also: damage-calculator. One could always check VCMI sources, but i'm not sure if it's 100% correspondce to homm3 system.

• Do you have an English version? Commented Jun 7, 2014 at 8:37

For spell power, here's a list of spells and how Power affects them.

# Duration (turns)

The number of turns these spells last in battle is equal to Power

• 🌪️Haste, Fortune, Precision, Air Shield, Protection From Air, Counterstrike, Magic Mirror
• 🔥Bloodlust, Curse, Protection From Fire, Blind, Misfortune, Fire Shield, Slayer
• ⛰️Shield, Slow, Stoneskin, Protection From Earth, Anti Magic, Sorrow
• 🌊Bless, Protection from Water, Weakness, Forgetfulness, Mirth, Prayer

# Damage

These spells do damage based on Power with a multiplier ranging from 5 to 75. The additional numbers indicate the effect of Basic/Advanced/Expert Magic in that area (Air, Fire, Earth, or Water).

• 🌪️🔥⛰️🌊Magic Arrow (power * 10 + 10/20/30)
• 🌪️Lightning Bolt (power * 25 + 10/20/50)
• 🌪️Destroy Undead (power * 10 + 10/20/50)
• 🌪️Chain Lightning (initial hit power * 40 + 25/50/100)
• 🔥Fire Wall (power * 10 + 10/20/50)
• 🔥Fire Ball (power * 10 + 15/30/60)
• 🔥Land Mine (power * 10 + 25/50/100)
• 🔥Armageddon (power * 50 + 30/60/120)
• 🔥Inferno (power * 10 + 20/40/80)
• ⛰️Death Ripple (power * 5 + 10/20/30)
• ⛰️Meteor Shower (power * 25 + 25/50/100)
• ⛰️Implosion (power * 75 + 100/200/300)
• 🌊Ice Bolt (power * 20 + 10/20/30)
• 🌊Frost Ring (power * 10 + 15/30/60)

# Health points affected

These spells use Power to determine how many health points of creatures are hypnotized, healed, or resurrected/reanimated.

• 🌪️Hypnotize (stack must have total health < single creature health * 25 + 10/20/50)
• 🌊Cure (heals power * 5 + 10/20/30)
• 🔥Sacrifice (resurrects health (power + destroyed troop's health + 3/6/10) * # sacrificed)
• ⛰️Animate Dead (reanimates health power * 50 + 30/60/160 [sic])
• ⛰️Resurrection (resurrects health power * 50 + 40/80/160)

# Range on map

For this spell, Power determines how far away on the map from the character the spell can function.

• 🌪️🔥⛰️🌊Visions (power * 1/2/3, minimum 3)

# Number summoned

The number of elementals summoned is based on Power and the level of magic (Basic/Advanced/Expert) for that type.

• 🌪️🔥⛰️🌊Summon Air/Fire/Earth/Water Elemental (summons power * 2/3/4)

# No effect

Power is not used to compute the effect of these spells.

• 🌪️View Air, Disguise, Disrupting Ray, Dimension Door, Fly
• 🔥Berzerk, Frenzy
• ⛰️View Earth, Quicksand, Earthquake, Force Field, Town Portal
• 🌊Dispel, Summon Boat, Remove Obstacle, Scuttle Boat, Teleport, Clone, Water Walk

The source of this info is these pages:

• +1 I reworded and reformatted a few bits of your post to make it a bit easier to read. Great answer!
– Wipqozn
Commented Sep 1, 2020 at 13:12

I have just created damage simulator for calculation, enjoy: HOMM3 Damage Simulator

• Thank you for contributing. This appears to be a useful tool that you have created, and I'm sure the OP will find your input helpful. It would be good to edit your answer and provide some explanation on how this tool makes its calculations. (Generally, answers that are contain only links are discouraged here.) Remember, not everyone here can access external sites, and links may break over time. Commented Jan 21, 2019 at 0:20