CS2 Trade-Up Contracts Explained: How They Work and When They Pay

A CS2 trade-up contract converts ten skins of one rarity into a single random skin of the next rarity up. Whether that's profit or donation is pure math: input cost versus the probability-weighted value of every possible output — and most casual trade-ups lose money to that math.

The mechanics in one minute

Put ten skins of the same rarity tier into the contract; receive one random skin of the next tier, drawn from the collections your inputs came from. Your inputs' collections set the possible outcomes; the proportion of inputs per collection weights the odds; and your inputs' average float maps onto the output's wear range.

The three numbers that decide everything

• Input cost — what the ten skins actually cost you to buy.
• Outcome table — every possible output skin, its probability, and its live market value.
• Expected value (EV) — the probability-weighted sum of outputs, minus the fee of the market you'd sell on. If EV after fees is below input cost, the trade-up is a paid lottery ticket.

Where trade-ups go wrong

• Valuing outputs at sticker price. An output "worth" a number you can't net after a ~13% sell fee isn't worth that number (see fees explained).
• Ignoring float mapping. High-float inputs can push the output into a cheaper wear tier and quietly wreck the EV — the float guide covers why tiers matter so much.
• Overpaying for inputs. The whole edge usually lives on the buy side: sourcing the ten inputs below cross-market consensus is what turns a neutral contract positive.
• One-shot thinking. EV is a long-run number. A single +EV contract can still lose; sizing across many contracts is how the math shows up.

When trade-ups actually pay

Profitable trade-ups are a sourcing game: find a collection whose commons are underpriced on one market while its rare outputs stay pricey and liquid, buy inputs at that discount, and keep the average float low enough for a favorable output wear. In other words — a trade-up is only ever as good as the prices you buy at. Cross-market comparison on the board is where cheap inputs get found; the same logic that powers arbitrage flips powers contract sourcing.

A sane way to start

Run your first contracts on paper: price the ten inputs, list the outcome table with live values, subtract sell fees, and see if the EV clears cost. If the paper version keeps losing, real money would too. When a contract does clear, source each input at its cheapest market rather than one convenient shop — that spread is your margin.

Frequently asked questions