Case Odds and the Expected Value of a CS2 Key

Valve disclosed approximate drop rates for weapon cases in 2017 to meet regulations in China, and those figures still guide how most players think about opening. Per case, the rarity odds sit close to these.

• ▸Mil-Spec at about 79.92 percent
• ▸Restricted at about 15.98 percent
• ▸Classified at about 3.20 percent
• ▸Covert at about 0.64 percent
• ▸A rare special item, meaning a knife or gloves, at about 0.26 percent

On top of that, any weapon drop carries about a one in ten chance of being StatTrak.

Opening a case costs the key plus the case itself. Valve sells keys at a fixed price in each currency, and the case price moves with the market. Add the two and you have the price of one roll.

Expected value tells you what an average opening returns over many attempts. You can calculate it for any case with public prices.

1. 1
   Take the average market price of the Mil-Spec skins in that case and multiply it by 0.7992
2. 2
   Do the same for Restricted with 0.1598, Classified with 0.032 and Covert with 0.0064
3. 3
   Take the average price of the knives or gloves in the case and multiply by 0.0026
4. 4
   Add the five results together
5. 5
   Compare the total with the cost of the key plus the case

For the cases people open most, the total comes out well below the cost of a roll. Most openings return a Mil-Spec skin worth a fraction of the key. The rare knife pulls the average up, but at odds of about one in 385, you should expect to open hundreds of cases to see one, and the specific knife you get may sit at the cheap end of the range.

If you want a specific skin, buying it costs you a known amount and gets you that item. Opening cases to chase it costs you an unknown amount, and the expected return sits below what you spend.

Opening has a place if you enjoy the roll itself and treat the cost as entertainment. Set that budget before you start, and keep it separate from money you mean to spend on skins.