Futures prices move in ticks, and tick size is the minimum price movement for a given contract.
The minimum tick size is basically “minimum price fluctuation” for a given futures contract. Because each product has its own notional value, the minimum tick size varies from product to product.
Tick sizes are defined by the exchange and vary depending on the size of the financial instrument and requirements of the marketplace. Tick sizes are set to provide for best liquidity and tight bid-ask spreads.
The minimum price fluctuation (and subsequent minimum tick size) for any contract can be found in the product specifications on the exchange’s website.
For example, the minimum tick size for WTI Crude Oil is equal to 1 cent, and the contract size is 1000 barrels. The minimum tick movement is therefore $10.
For the micro e-mini S&P 500 index future, the minimum price fluctuation (the minimum tick size) is .25 index points, and each .25 movement = $1.25.
For CME Group, tick size and minimum price movement for each contract can be found in the contract specs.