A lot size in forex refers to the standardized quantity of currency units being traded in a transaction. It is a way to measure the size of a trade efficiently. The most common lot sizes are:

• Standard Lot : 100,000 units of the base currency
• Mini Lot : 10,000 units
• Micro Lot : 1,000 units
• Nano Lot : 100 units

For example, trading one standard lot of EUR/USD means you are trading €100,000 against the equivalent amount in US dollars

. Lot sizes help determine the value of each pip movement, which directly affects potential profits or losses. Traders can choose different lot sizes depending on their risk tolerance and account size. Beginners often start with micro or nano lots to limit risk, while professional traders may use standard lots for larger trades

. In summary, a lot size is the fixed amount of currency units you buy or sell in forex trading, with 100,000 units being the standard size, and smaller lots available for more precise control and risk management