Now you understand what contracts for difference are, it’s time to take a look at how they work. Here we explain four of the key concepts behind CFD trading: spreads, deal sizes, durations and profit/loss.

1、Spread and commission

CFD prices are quoted in two prices: the buy price and the sell price.

• The sell price (or bid price) is the price at which you can open a short CFD

• The buy price (or offer price) is the price at which you can open a long CFD

Sell prices will always be slightly lower than the current market price, and buy prices will be slightly higher. The difference between the two prices is referred to as the spread.

Most of the time, the cost to open a CFD position is covered in the spread: meaning that buy and sell prices will be adjusted to reflect the cost of making the trade.

The exception to this is our share CFDs, which are not charged via the spread. Instead, our buy and sell prices match the price of the underlying market and the charge for opening a share CFD position is commission-based. By using commission, the act of speculating on share prices with a CFD is closer to buying and selling shares in the market.

2、Deal size

CFDs are traded in standardised contracts (lots). The size of an individual contract varies depending on the underlying asset being traded, often mimicking how that asset is traded on the market.

Silver, for example, is traded on commodity exchanges in lots of 5000 troy ounces, and its equivalent contract for difference also has a value of 5000 troy ounces. For share CFDs, the contract size is usually representative of one share in the company you are trading. To open a position that mimics buying 500 shares of HSBC, you’d buy 500 HSBC CFD contracts.

This is another way in which CFD trading is more similar to traditional trading than other derivatives, such as options.

3、Duration

Most CFD trades have no fixed expiry – unlike options. Instead, a position is closed by placing a trade in the opposite direction to the one that opened it. A buy position of 500 gold contracts, for instance, would be closed by selling 500 gold contracts.

If you keep a daily CFD position open past the daily cut-off time (typically 10pm UK time, although this may vary for international markets), you’ll be charged an overnight funding charge. The cost reflects the cost of the capital your provider has in effect lent you in order to open a leveraged trade.

This isn’t always the case though, with the main exception being a forward contract. A forward contract has an expiry date at some point in the future, and has all overnight funding charges already included in the spread

4、Profit and loss

To calculate the profit or loss earned from a CFD trade, you multiply the deal size of the position (total number of contracts) by the value of each contract (expressed per point of movement). You then multiply that figure by the difference in points between the price when you opened the contract and when you closed it.

Profit or loss =(no. of contracts x value of each contract)x (closing price - opening price)

For a full calculation of the profit or loss from a trade, you’d also subtract any charges or fees you paid. These could be overnight funding charges, commission or guaranteed stop fees.

Say, for instance, that you buy 50 DJ30 contracts when the buy price is 26500.0. A single DJ30 contract is equal to a $5 per point, so for each point of upward movement you would make $250 and for each point of downward movement you would lose $250 (50 contracts multiplied by $5).

If you sell when the DJ30 is trading at 26510, your profit would be $2500

2500 = (50 x 5) x (26510 - 26500.0)

If you sell when the DJ30 is trading at 26495.0, your loss would be $1250

-1500 = (50 x 5) x (26495.0 - 26500.0)