Combat Calculator

Attack composition & effective defense

Each defense column is weighted by that troop type’s share of the attacking strength, then multiplied by the wall bonus.

Troop attack

Count × base attack × (1 + terrain attack % / 100 + division attack % / 100).

Commander attack

Minimum of raw troop attack across the attacking army and base commander attack × (1 + 6 × Heroism level). Apply the commander’s troop-type terrain and division attack modifiers afterward.

Defense against each type

Count × base defense against that type × (1 + terrain defense % / 100) × (1 + division defense bonus against that type / 100). Terrain follows the defender’s own troop type. A defending commander contributes one base unit.

Effective defense

Sum of each defense value × its attacking type’s share of total attack, then × (1 + wall bonus % / 100).

Attacker casualties

For each troop entry: min(count, floor(count × effective defense ÷ total attack)).

Defender casualties

For each troop entry: min(count, floor(count × total attack ÷ effective defense)).

Rounding & ties

Round losses down per unit within each division. Keep intermediate strengths exact. Equal strengths mean mutual troop destruction. This precision rule differs from the source calculator’s intermediate rounding.

• Enter troop counts separately from the commander. Leaving the commander empty omits their strength and division bonuses.
• Division bonuses are effective percentages. Include any applicable innate or elite effect yourself; the calculator does not apply those effects again.
• One attacking army and one defending force, with up to five divisions per side and one million troops per unit entry. These are calculator limits.
• Player and normal four-type NPC troops may share a force. NPC-containing divisions do not accept commanders or division bonuses. Equipment, personal defensive skills, magic, prestige, raid or siege resolution, XP, resource valuation, and commander casualties remain outside the model.
• Player statistics use the preserved official race-page snapshot. NPC statistics use the reviewed 558-record client catalog; ten zero-stat or siege records remain visible in Reference but cannot be calculated. Terrain uses the official table reviewed September 15, 2026, including the April 2026 plains changes.
• Force templates are saved only in this browser. Pasted report text is parsed locally and is never saved or sent; only the resulting force is sent when you calculate.
• The community casualty and commander rules still need validation against recent in-game battles.

• Stardance’s Illyriad Battle Calculator — community calculation reference; independent implementation.
• Official terrain modifiers — plains cavalry attack +20%, cavalry defense +15%, spear defense 0%.
• Player-unit reference · NPC-unit reference · Terrain reference. The calculator uses all three versioned tables.

Model qm-combat-estimate-2 · Player troops: official-races-2025-06 · NPC troops: illyriad-unitjs48-2026-08-29 · Terrain: illypedia-terrain-2026-09-15.