Definition
Case opening odds are the probabilities Valve assigns to each rarity tier when a weapon case is opened in CS2. Five tiers, five percentages, summing to 100%. Valve published the exact figures on the Counter-Strike blog in 2017 to comply with regional gambling-disclosure rules, and the numbers have not moved since.
The five tiers, with the official percentages
| Tier | Rarity | Drop chance | Roughly |
|---|---|---|---|
| Mil-Spec (blue) | weakest in the case | 79.92% | 4 in 5 openings |
| Restricted (purple) | mid | 15.98% | 1 in 6 openings |
| Classified (pink) | high | 3.20% | 1 in 31 openings |
| Covert (red) | top weapon skin | 0.64% | 1 in 156 openings |
| Rare Special Item (knife or glove) | gold | 0.26% | 1 in 387 openings |
Each tier is exactly five times rarer than the one below it. That ratio is hard-coded into the case-opening logic and is the same for every weapon case shipped since 2013.
What the percentages do not tell you
Three things stay invisible in the headline numbers:
- Which skin inside a tier you get — uniform within the tier. If a Mil-Spec tier has seven skins, each lands roughly one-seventh of the 79.92%.
- Whether the skin is StatTrak — a separate 10% roll on top, applied to every weapon drop. Knife and glove drops are also StatTrak-eligible at the same 10%.
- The exterior — independent uniform-random float draw at drop time. See the float value entry for how that maps onto FN/MW/FT/WW/BS.
Why these numbers drive expected value
Multiply each tier's percentage by the average market value of the skins in the tier, sum, and you get the expected value of one opening. For most active cases that figure sits well below the cost of the case + key. The full math walked through on three popular cases is in the real expected value of opening CS2 cases. The pillar context — what the drop pool is, how cases ship, why discontinued cases behave differently — lives in the cases pillar guide.