The contract size of most equity option contracts is 100 shares. However, the contract size for commodities and financial instruments such as currencies and interest rate futures varies widely. For example, the contract size for a Canadian dollar futures contract is C$100,000, while the size of a soybean contract traded on the Chicago Board of Trade is 5,000 bushels.
The size of a gold futures contract on the COMEX is 100 ounces. Therefore, each $1 move in the price of gold translates into a $100 change in the value of the gold futures contract.