A CS2 trade-up pays off only when the expected value of all its results, after selling fees, is higher than what the inputs cost. Price every possible result, not just the one you want, and know how much the worst one loses. The contract rules are in the trade-up guide; this page is the check to run before you buy inputs.
Which recipe you are using
| Recipe | Inputs | Result |
|---|---|---|
| Ten-skin contract | 10 weapon skins of the same rarity, all normal or all StatTrak™ | One skin of the next rarity from a collection among the inputs |
| Covert contract | 5 Covert skins | A knife or gloves from the inputs’ collections |
| StatTrak™ Covert contract | 5 StatTrak™ Covert skins | A StatTrak™ knife from the inputs’ collections |
Valve’s Trade Up Contract article covers the ten-skin recipe: Souvenir weapons can go in, the result is not Souvenir, and a skin that is already the rarest in its collection can’t be used. Valve’s 22 October 2025 update added the five-Covert recipes, which the support article does not list yet. Souvenir inputs came with the 21 May 2026 update.
Step 1: list every result and its chance
Our calculator gives each collection a share equal to its number of inputs divided by the contract size, then splits that share evenly among the collection’s possible results. Example: seven inputs from collection A, which has two possible results, and three from collection B, which has three.
| Result | Calculation | Chance |
|---|---|---|
| A1 | (7 ÷ 10) ÷ 2 | 35% |
| A2 | (7 ÷ 10) ÷ 2 | 35% |
| B1 | (3 ÷ 10) ÷ 3 | 10% |
| B2 | (3 ÷ 10) ÷ 3 | 10% |
| B3 | (3 ÷ 10) ÷ 3 | 10% |
A cheap filler from a third collection adds that collection’s results to the pool, so price them too. Five-Covert contracts use a different weighting for knife and glove finishes; the methodology explains both models.
Step 2: put a sale price on every result
Use what each result sells for at its predicted wear, not the cheapest listing. The predicted wear comes from the input floats; the float guide shows how. If the calculator shows $0.00 for a result, its price is missing, not zero: look the skin up in the price table before you trust the expected value.
Step 3: take the fee off and compare with the input cost
Example: the ten inputs cost $100. There is a 25% chance of a result that sells for $200 and a 75% chance of one that sells for $80. The marketplace takes 10% of each sale.
| Result | Chance | Sale price | After fee | Weighted |
|---|---|---|---|---|
| High | 25% | $200 | $180 | $45 |
| Low | 75% | $80 | $72 | $54 |
Before fees the expected value is 0.25 × $200 + 0.75 × $80 = $110, which looks like a $10 profit. After the fee it is $45 + $54 = $99: an expected loss of $1 on every $100 contract. The inputs would have to cost less than $99 to break even, and every dollar of checkout or withdrawal cost moves that line down.
Our calculator’s expected value uses its price estimates before selling fees, so take your marketplace’s fee off yourself. The fee comparison calculator shows the fee for each marketplace, and the marketplace fee guide lists them side by side.
Step 4: decide what you can afford to lose
- Worst result. In the example the low result returns $72 on $100: a $28 loss on that contract.
- One contract, one result. Expected value is the average over many contracts. A single contract pays one result.
- Time to sell. Check how many copies of each result sell on Steam per month on its skin page before you count on a quick sale.
Checklist before you buy the inputs
- Every input: exact name, normal or StatTrak™, collection, float and price.
- Every result: chance, predicted wear and a realistic sale price.
- Expected value after fees against the total input cost.
- The loss on the worst result.
Build the contract in the trade-up calculator, or start from a ready contract in the trade-up finder.