18+ only. These sites are not for players under 18 or where skin gambling is prohibited, including the UK. Valve's Steam terms do not allow using Steam for gambling, and accounts or trades can be restricted. Some links are affiliate links.
A case is a price, a list of items and a probability for each item. Those three things are enough to work out what a case returns on average. The numbers below are made up to show the arithmetic. They are not from any site.
The formula
EV = sum of (item value x item probability)
House edge = 1 - EV / case price
A worked example
| Item | Value | Probability | Value x probability |
|---|---|---|---|
| Common skin | $0.50 | 80% | $0.40 |
| Mid skin | $3.00 | 18% | $0.54 |
| Rare skin | $40.00 | 2% | $0.80 |
EV is $1.74. If the case costs $2.00, the house edge is 13%, so you lose 26 cents per case on average. Most openings return far less than the average, because the rare item carries almost half of the EV.
Check a case yourself
- Find the probability for every item. If the site lists only rarity groups, you cannot finish the sum.
- Check that the probabilities add up to 100%.
- Take the value of each item from the site's own sell-back price, not from a market price you cannot get.
- Run the sum, then compare EV with the case price.
- Read the withdrawal rules. A value you cannot withdraw is not worth its listed price.
Calculator
Paste one item per line as value probability, for example 0.50 80. It runs in your browser and sends nothing anywhere.
Compare what sites publish in the case odds tables.