I just realized that swap means a fee higher than I thought. What’s going on? If you trade but don’t close your order within the same day, the swap will quietly eat away at your profit every night.

Actually, swap refers to the overnight interest—specifically, the interest rate differential across currencies. When you trade EUR/USD, you’re “borrowing” USD and “buying” EUR. Each country’s central bank has different interest rates. The FED of the US and the ECB of Europe have different rates. That difference is the source of swap.

If you Buy EUR/USD and the Euro’s interest rate is higher than the dollar’s, you may receive a positive swap. But if it’s lower, you’ll have to pay. Brokers will also add their own handling fee, so the swap you actually receive is often less than expected—or even negative on both sides.

The most important thing to watch out for is the 3-Day Swap. When the market closes on Saturday and Sunday, interest keeps accruing, but the market isn’t operating. So brokers have to collect and calculate it all over 3 days in a single night—usually on Wednesday night. If you hold an order over that period, the swap will be tripled.

Calculating swap isn’t difficult if you know how. If your broker shows it as a percentage, take the total position value (not the margin) and multiply it by the specified swap rate. For example, if you trade 1 Lot EUR/USD at 1.0900, the total value is 109,000 USD. If the Long swap is -0.008% per night, you’ll pay 8.72 USD per night.

It seems small, but if you use Leverage 1:100, you might only put up 1,090 USD in Margin. That means the swap is effectively eating 0.8% of your Margin every night. If the market stays flat for several days, the swap can close your position even if the price hardly moves.

But swap isn’t just a risk—it can also create opportunities. Carry Trade is about profiting from the interest rate differential. If you Buy a currency pair with Positive Swap, you’ll get money credited to your account every night. This is suitable for Position Traders who hold orders for a long time. The risk is that the price could move against you and wipe out all the swap gains.

Another option is a Swap-Free account or an Islamic account. If you want to hold orders for weeks or months without worrying about swap, the Spread may be slightly wider, but it can be worth it for a Swing Trader.

Before placing an order, always check the swap value first. On platforms like MT4/MT5, go to Market Watch, right-click, and select Specification. For Mitrade and newer brokers, it’s often clearly shown on the trading page under “ค่าธรรมเนียมข้ามคืน” (overnight fees).

In summary, swap means an embedded cost that’s higher than you think. If you’re a Scalper, you don’t need to worry too much. But if you hold orders for a long time, you need to plan carefully—choose the side with Positive Swap or use a Swap-Free account. Otherwise, swap will gradually erode your profits.