Conclusion
Unciv's damage formula (BattleDamage.kt) depends on one number: the ratio of attack strength to defense strength after all bonuses. At equal strength each side deals 24–36 damage. The stronger side's damage grows quickly with the ratio, while the weaker side's shrinks.
Two things worth knowing: the random roll is fixed by the turn and tile, so reloading doesn't change the result; and a wounded unit deals less damage — 1% less for every 3 HP it's missing.
Damage Calculator
Attacker
Defender
| Attack / Defense / Ratio | / / |
| Damage to defender | |
| Damage to attacker | |
| Kill this turn? |
Uses the game's formula: ratio = attack ÷ defense; stronger/weaker ratio s; multiplier m = (((s + 3) ÷ 4)4 + 1) ÷ 2; damage = (24 + 12 × roll) × m (or 1/m for the weaker side) × (1 − missing HP ÷ 300). Put promotion, policy and other bonuses into the “other bonuses” boxes.
Combat Modifiers (from the Code)
| Modifier | Value | Notes |
|---|---|---|
| Fortified | +20% per turn, up to +40% | Builds up over 2 turns of not moving. |
| Terrain (defender) | Hill/forest/jungle +25%, marsh −15%, flood plains/oasis −10% | The best feature replaces the base terrain; embarked units get none. |
| Flanking | +10% per other friendly melee unit next to the defender | Melee attacks only. Some policies and promotions raise it (Hussar +50%). |
| Attacking across a river | −20% | Melee only, unless both tiles are road-connected after the right tech. |
| Amphibious / naval landing | −50% | Embarked units attacking land, or naval melee units attacking a land unit. |
| Missing strategic resource | −25% | When you're short of the resource a unit needs. |
| Great General nearby | +15% | Within 2 tiles (China doubles it). |
| Vs barbarians | +75% to 0% by difficulty | See Difficulty. |
| Wounded attacker/defender | −1% damage dealt per 3 HP missing | Japan's units ignore this. |
Practical Takeaways
- Stack defense bonuses. A unit fortified for 2 turns on a hill gets +65% defense — enough to turn an even fight into a lopsided one.
- Attack with healthy units. A unit at 40 HP deals 20% less damage than at full health.
- Surround before you strike. Each other melee unit next to the target adds 10% to every melee attack.
- Soften with ranged units first. Ranged attackers take no retaliation (air units are the exception).
- Don't attack over rivers or from boats if you can avoid it: −20% and −50%.
FAQ
Can I reload to get a better roll?
No. The roll comes from the turn number and the tile position, so the same attack on the same turn gives the same result.
Do civilians take damage?
A civilian defender always takes 40 damage (and is usually captured).
How do I see a unit's bonuses?
The in-game battle preview lists every modifier; add the ones that aren't covered here into the “other bonuses” boxes.
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More Unciv guides
Unciv guide home · All 34 Civilizations · City Growth and Happiness · City-States: Bonuses and Quests · Difficulty Levels Explained · Early Game: Key Numbers and Ancient Ruins · Every Building: Cost, Upkeep and Effects · Every Promotion and Effect · Every Religion Belief · Every Unit's Stats by Era · Every World and National Wonder · Game Speed and Starting Era · Great People: Points and the Shared Pool · Mods: Installing and Popular Picks · Multiplayer: Playing Online · Social Policies and Policy Cost · Tech Tree: Every Tech and Unlock · Terrain, Resources and Improvements · Unciv vs Civilization V · Victory Conditions