diff --git a/ui/main_window.py b/ui/main_window.py
index 8813b65..c355dab 100644
--- a/ui/main_window.py
+++ b/ui/main_window.py
@@ -1191,25 +1191,15 @@ class MainWindow(QMainWindow):
                     self.hud.on_damage_taken(Decimal(str(damage)))
                     
                     # Calculate armor decay based on actual damage absorbed
-                    # Formula: Decay (PEC) = damage_absorbed * 0.05 * (1 - durability/100000)
-                    # Approximate: ~0.05 PEC per damage point for non-L armor
-                    # For simplicity: 0.0005 PED per damage point (0.05 PEC = 0.0005 PED)
-                    if self._selected_armor_stats and 'decay' in self._selected_armor_stats:
-                        # Use decay per hit from armor stats if available
-                        armor_decay_pec = Decimal(str(self._selected_armor_stats.get('decay', 0)))
-                        # Approximate: decay scales with damage
-                        # Most armor has ~0.05 PEC decay per damage point
-                        decay_per_damage = Decimal('0.0005')  # 0.05 PEC = 0.0005 PED
-                        cost_ped = Decimal(str(damage)) * decay_per_damage
-                        if cost_ped > 0:
-                            logger.debug(f"[HUD] update_armor_cost({cost_ped:.4f}) based on damage {damage}")
-                            self.hud.update_armor_cost(cost_ped)
-                    else:
-                        # Fallback to simple calculation
-                        cost_per_hit = self._session_costs.get('cost_per_hit', Decimal('0'))
-                        if cost_per_hit > 0:
-                            logger.debug(f"[HUD] update_armor_cost({cost_per_hit}) [fallback]")
-                            self.hud.update_armor_cost(cost_per_hit)
+                    # EU Formula: Decay (PEC) = damage_absorbed * 0.05 * (1 - durability/100000)
+                    # For (L) armor at full TT: ~0.05 PEC per damage point
+                    # For adjusted armor: decay varies by piece
+                    # Based on user feedback: ~0.00025 PED per damage (0.025 PEC)
+                    decay_per_damage = Decimal('0.00025')  # ~0.025 PEC per damage
+                    cost_ped = Decimal(str(damage)) * decay_per_damage
+                    if cost_ped > 0:
+                        logger.debug(f"[HUD] update_armor_cost({cost_ped:.4f}) based on damage {damage}")
+                        self.hud.update_armor_cost(cost_ped)
             except Exception as e:
                 logger.error(f"[ERROR] Error in on_damage_taken: {e}")
                 import traceback