Swap
Swap, or rollover, is the amount debited or credited for holding a position open across the trading-day rollover. It comes from the interest rate difference between the pair's two currencies plus the broker's markup, and it enters the trade's net result. Run this calculation now: profit and loss calculator
Where swap comes from
Buying a pair is, in practice, buying the base currency and selling the quote currency. If the currency bought yields more interest than the one sold, the difference is credited; if it yields less, it is debited. The broker adds its own markup on top, which is why swap is often negative in both directions on many pairs.
At most brokers, Wednesday charges triple swap, to cover the weekend when the interbank market does not settle.
How much it weighs on the result
Swap is irrelevant on a trade of minutes and decisive on one of weeks. A swap of −8 per lot per night on a 0.5-lot position over 10 nights costs 40 — on a trade whose target was 100, that is 40% of the result.
In the profit and loss calculator, accumulated swap goes in the costs field together with commission. 'Swap-free' (Islamic) accounts replace swap with a flat fee after a few days; the cost changes its name, not its existence.
FAQ
Can swap be positive?
It can, when the currency bought pays much higher interest than the one sold and the broker's markup does not eat the difference. It is the basis of the carry trade.