Combat Loss Calculator

Calculate OpenFront combat losses. Enter attacking and defending troops, terrain, and defense post coverage — it returns per-tile losses, the exchange ratio, and how many tiles the attack takes, using the game's own formula.

Map Map size Attacking troops Defender troops Defender land (leaderboard %) Your land (leaderboard %) Terrain you push into Inside defense post range Defender is a traitor Defender is a bot

Your loss per tile–

Defender loss per tile–

Exchange ratio (yours ÷ theirs)–

Tiles this attack takes–

Troops left when it ends (you / them)–

Min-loss attack size (1.67× defender)–

Troops are internal values — the on-screen and leaderboard numbers are 1/10 of internal, so multiply what you read by 10. As the defender's troops drop, per-tile losses change every tile, so "tiles taken" runs the same loop the game does instead of multiplying. Fallout is not modeled.

Formula used

attackerLoss = mag * traitorMod
             * (0.463 * ratioTerm + 0.0039 * densityTerm)

ratioTerm   = clamp(defTroops/atkTroops, 0.6, 2)
              * sizeDebuff * largeAttackerPenalty
densityTerm = defTroops / defTiles

defenderLossPerTile = defTroops / defTiles
mag: plains 80 · highland 100 · mountain 120
     · defense post ×5 · vs bot ×0.7

Attacker loss is the sum of two terms — a troop-ratio term and a defender-density term. The ratio is clamped to 0.6–2, so pouring in more than 1.67× the defender's troops stops lowering your per-tile loss. The clamp multiplies both terms, so the balance between them ignores your troop count entirely — it is set by how thickly the defender stacked: at 1 troop/tile the density term is 1% of your loss, at 100 troops/tile it reaches 46%. That is why an enemy spread thin over a big empire is cheap to cut.

Full explanation: the combat formula →

What attack ratio should you use? →