According to the loot table ( http://picacid.com/arma2/loot_en.html ) in a military barracks: 12 loot piles 0.40 chance of an item spawning in a loot pile 0.11 chance of an NVG spawning in a loot pile that spawned an item The odds of getting a NVG in a barracks is equal to 100% minus the odds of not getting an NVG in a barracks. So, the odds of not getting an NVG in any loot pile is: 1 - (0.40 * 0.0011) = 0.99956 Now the odds of not getting an NVG in a barracks is: (1 - (0.40 * 0.0011)) ^ 12 = 0.99473 Now all we need to do to get the chances of an NVG spawning in a barracks is subtract our previous result by 100%. 1 - ((1 - (0.40 * 0.0011)) ^ 12) = 0.00526 So we have a chance of 0.526% chance of getting an NVG in a barracks. Now, what is the chance of getting a pair of NVG given that we visit N barracks? 1 - ((1 - (0.40 * 0.0011)) ^ (12 * N)) So, visiting a barracks 100 times would give you a ~41% chance of getting a single NVG.