ITEMS / REVIEWED 2026-11-11
CS2 trade-up contracts: odds and float math
See how collection shares and normalized float affect a contract result, without invented prices.
STEP 01
Standard contracts
A standard contract exchanges ten eligible items of one rarity for one item one rarity higher. In the calculator, each input contributes to the chance of an output collection; each candidate next-tier skin divides that collection’s share.
STEP 02
Float mapping
Normalize each input float to its own skin range: (float − minimum) ÷ (maximum − minimum). Average those normalized values, then map the average across the possible output skin’s wear range.
STEP 03
Covert and Souvenir updates
Valve’s October 2025 update added five-Covert contracts: regular inputs may return a knife or gloves; five StatTrak inputs return a StatTrak knife. In May 2026, Valve added Souvenir inputs; their Souvenir attributes are removed, and the output is a normal item.
STEP 04
Verify before committing
The calculator does not contain a live inventory database, market prices, collection eligibility or expected value. Supply verified game-data counts yourself and check the live in-game contract screen before confirming.
Quick checklist
- Verify eligible items, quality and collections in the game.
- Normalize every input float against that skin’s own min/max range.
- Count each eligible next-tier outcome for every collection.
- Compare the model with the live contract screen before confirming.