I’ve been in Forex for years, and I swear that the very first thing I would’ve wanted to understand well is what a lot size is in trading. It’s not complicated, but it’s fundamental. So I’m going to try to explain it in the clearest way possible.

Basically, lot size in trading is the unit of measurement we use to standardize currency trades. Imagine that instead of lots, we had to manually write in every order something like “three hundred twenty-seven thousand eight hundred twelve euros in EUR/USD.” It would be chaos. That’s why the lot exists: it’s simply a pre-set package of units of the base currency.

In Forex, a standard lot equals 100,000 units of the base currency. If you trade EUR/USD with 1 lot, you’re investing 100,000 euros. With 2 lots, it’s 200,000, and so on. Now, not everyone has that much capital available, and that’s where mini lots and micro lots come in.

A mini lot is 10,000 units (represented as 0.1), and a micro lot is 1,000 units (0.01). Most beginner traders start with micro lots because the risk is more manageable. The difference between these three types is crucial: the larger the lot size, the higher the potential risk, but also the higher the potential profit. The smaller the lot size, the lower the risk and the lower the profit.

Now, what is lot size in trading from a calculation point of view? It’s pretty straightforward. If you want to open a position of 300,000 dollars in USD/CHF, you write 3 lots. If you want 20,000 pounds in GBP/JPY, you write 0.2 lots. If you want 7,000 Canadian dollars in CAD/USD, you write 0.07 lots. With practice, you do it without thinking.

But here’s the interesting part: lot size is directly related to pips, which are percentage points. One pip equals 0.01%, and it’s normally the fourth decimal place in currency pairs. When EUR/USD moves from 1.1216 to 1.1218, you’ve gained or lost 2 pips. The relationship between lot size and pips is what determines whether you make or lose money.

There’s a basic formula: Number of lots × 100,000 × 0.0001 × number of pips = profit or loss. But there’s a more intuitive method using equivalences. For each pip that moves in your favor in one lot, you earn 10 euros. In a mini lot, you earn 1 euro. In a micro lot, you earn 0.1 euro. So if you trade 3 lots and the market moves 4 pips in your favor, you make 3 × 4 × 10 = 120 euros.

Now, many people ask: how do I trade lots if I don’t have 100,000 euros? The answer is leverage. Most brokers offer leverage, which means that with 500 euros of real money, you can control a position of 100,000 euros if the leverage is 1:200. This amplifies both gains and losses, so you have to be cautious.

Choosing the right lot size is where real risk management comes in. First, define how much maximum capital you want to risk per trade. If your account has 5,000 euros and you want to risk a maximum of 5%, that’s 250 euros. Then place a Stop-Loss at a reasonable distance—say 30 pips. Now apply the formula: (Capital at risk ÷ (Stop-Loss distance × pip unit value)) ÷ 100,000. In this case, (250 ÷ (30 × 0.0001)) ÷ 100,000 = 1.25 lots.

The most dangerous thing about not managing what a lot size in trading is properly is ending up in a margin call. If you trade with leverage and the market moves against you, your available margin gets used up quickly. When it gets close to 100% of the committed margin, the broker alerts you. If you don’t close positions or deposit more money, the broker automatically closes your positions. I’ve seen traders lose everything for not respecting this.

My advice: spend time calculating your optimal lot size based on your capital and your risk tolerance. Always use a Stop-Loss. And please don’t get carried away by euphoria when you win a couple of trades. Discipline in lot sizing is what separates traders who last from those who disappear quickly.