I just noticed that many beginner traders don’t understand how to calculate lot size in forex, and that costs them money. It’s one of those topics that seems complicated at first but is quite logical once you break it down.

Basically, in forex you don’t buy units like in stocks. You work with lots, which are standardized packages. One lot is 100,000 units of the base currency. If you want to trade with euros, one lot is 100,000 euros. But here’s the interesting part: you don’t need to have all that money in your account thanks to leverage. With 1:200 leverage, you only need 500 euros to control a 100,000 lot.

Now, not everyone trades full lots. There are mini lots (10,000 units) and micro lots (1,000 units), which are much safer to start with. When you place your order, the system interprets the decimals: 1 is a full lot, 0.1 is a mini lot, 0.01 is a micro lot.

To calculate lot size in forex based on what you want to invest, it’s simple. If you need a position of 45,000 euros in EUR/USD, divide by 100,000 and you get 0.45 lots. With 20,000 pounds in GBP/JPY, it would be 0.2 lots. Practice makes you do it automatically.

What’s important is understanding the relationship between lot size and pips. Pips are price movements, usually the fourth decimal. If you invest 3 lots and the price moves 4 pips in your favor, the profit is 3 x 4 x 10 = 120 euros. With 0.45 lots and 8 winning pips: 0.45 x 8 x 10 = 36 euros. The formula is straightforward.

The critical thing is to select an appropriate lot size before opening a position. If your account has 5,000 euros and you decide to risk a maximum of 5% per trade (250 euros), and you set your stop loss 30 pips away, then your optimal lot size would be around 1.25 lots. This protects you from surprises.

Many traders fall into margin call because they don’t respect this. Leverage is a double-edged sword. When the market moves against you, your margin is consumed quickly. If it reaches 100%, the broker automatically closes your positions. I’ve seen it happen.

My advice: before trading, carefully calculate your lot size, set a coherent stop loss, and don’t let greed take over. That’s what separates traders who last from those who disappear.