Contract Size: What a Lot Really Represents

In forex, a standard lot is defined as 100,000 units of the base currency. A mini lot is 10,000 units and a micro lot is 1,000 units. This is why pip values in forex are fairly predictable once you know the lot size — the contract size is consistent across every currency pair, so the math scales cleanly.

Outside of forex, "one lot" stops meaning a fixed number of currency units and instead refers to a fixed number of units of whatever the underlying instrument is, and this is where beginners get tripped up. For gold, commonly traded under the symbol XAUUSD, one standard lot typically represents 100 troy ounces of gold, not 100,000 dollars of exposure. A one-dollar move in the gold price on a one-lot position therefore changes your profit or loss by 100 dollars, which surprises traders who assumed gold behaved like a currency pair.

Indices are even more varied because there is no universal standard. One lot on an index CFD, such as a contract tracking the S&P 500 or the German DAX, might represent a contract size where each 1-point move equals 1 dollar or 1 euro per lot, but the exact multiplier is set by the broker and can differ from one broker to another for the exact same index. Some brokers quote index CFDs in units where one lot equals one contract at a fixed value per point; others scale it differently. There is no substitute for checking the contract specification for the specific instrument and broker before sizing a trade.

The practical lesson is that contract size, not lot count alone, determines your real dollar exposure. Two traders each holding "one lot" of two different instruments can have wildly different risk, so always look up the contract specification — usually found in the platform's symbol information window — before assuming a lot means the same thing everywhere.