Contract size specifies the quantity of an underlying asset or the face amount represented by one derivative contract. It converts a contract count into economic exposure. One contract is not necessarily one coin, and identically named assets can have different contract sizes across products or venues.
Read the unit behind the count
Suppose a linear contract represents 0.01 BTC. Holding 100 contracts represents 1 BTC of underlying exposure; at a valuation price of 50,000 USDT per BTC, the notional is 50,000 USDT. This hypothetical calculation excludes fees and says nothing about the collateral required.
An inverse product may instead define each contract by a fixed dollar face amount. Its value expressed in coin changes with price. For index products, a currency amount per index point may supply the conversion. The product’s size and multiplier definitions must be read together.
Do not confuse size with order limits
Contract size differs from minimum order quantity, the permitted quantity increment and the maximum position limit. An interface may accept underlying-asset quantities directly instead of displaying contract counts, so its input unit also matters.
Changing the number of contracts changes exposure and the value of a price move. Leverage changes the margin relationship, not what one contract represents. Comparing products requires checking contract size, quote units, settlement currency and payoff structure before comparing their displayed prices.