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Methodology
The Skinbase CS2 case ROI calculator estimates how much value a case opening returns on average. It combines the full opening cost, published CS2 drop rates, every possible item, and current marketplace prices. The result helps you compare cases on the same scale before you spend money, but it does not predict what any single opening will contain.
First, Skinbase calculates the total opening cost: the current case price plus the fixed $2.50 key price. It then calculates the average unbox value, also called expected value or EV. Each outcome adds its market price multiplied by its probability, so common low-value skins and extremely rare knives or gloves are weighted according to how often they can drop.
Standard weapon cases use the published rarity distribution below. Items within a rarity share that tier's probability, while StatTrak-capable weapon finishes have a separate 10% StatTrak chance.
The calculation goes beyond a simple rarity average. Skinbase weights prices by each skin's float range and likely wear, separates normal and StatTrak variants, and accounts for priced rare phases such as Doppler finishes. The methodology follows the .
Answers to the most common questions about CS2 ROI, expected value, and trade ups.
Expected value
EV = Σ(outcome probability × current outcome price)
Return shown
ROI = expected value ÷ total opening cost × 100
Skinbase displays ROI as the percentage of your opening cost that you can expect to receive back over many openings. A 100% result is break-even. A 60% result means an average return of $0.60 for every $1.00 spent, or an expected loss of 40% before selling fees.
For example, suppose a case and key cost $5.00 in total and the probability-weighted value of all drops is $3.00. The calculator shows 60% ROI: $3.00 ÷ $5.00 × 100. The expected shortfall is $2.00 per opening, even though an individual lucky drop could be worth much more than $5.00.
ROI and profit chance answer different questions. ROI is the probability-weighted, long-run return across every possible drop. Profit chance is the combined probability of receiving an item currently worth more than the case and key together. A case can therefore have a relatively strong ROI but a low profit chance when a very small number of expensive outcomes contribute a large share of its expected value. Compare both numbers rather than treating either one as a promise of profit.
You can also browse the complete CS2 case catalog or compare a more controlled set of possible outcomes with the CS2 trade-up calculator.
Skinbase keeps case comparisons transparent: you can see the costs, probabilities, prices, and assumptions behind the result instead of relying on one unexplained percentage.