定義
Tick size
マーケットにおける最小の価格刻み幅。
Tick size
Definition
The Polymarket tick size is the minimum price increment at which outcome prices can move on the CLOB. It determines the smallest allowable difference between two adjacent prices on an order book and therefore constrains quoting and execution granularity.
In practice
On Polymarket the tick size is usually $0.01. When prices approach extreme values the tick tightens to $0.001 — specifically when an outcome price moves above $0.96 or below $0.04. This tighter tick near the edges reduces discretisation error when prices represent near-certain or near-impossible outcomes.
How you see it
You encounter tick size in the order book and when placing limit orders: the CLOB enforces prices that are multiples of the current tick. The Market WebSocket emits tick_size_change events when the allowable increment changes.
Why it matters
- Liquidity and spreads: A larger tick can widen quoted spreads because bids and asks must sit on coarser grid points. A smaller tick allows tighter quoting and finer price discovery.
- Execution granularity: Tick size limits the smallest price improvement you can post as a maker or chase as a taker.
- Strategy impact: Arbitrage and market-making strategies must account for the tick to calculate realisable edges and expected slippage.
See also
- /glossary/clob