# How does purchasing your own country's currency as part of a currency pair work?

For instance, if the USD/JPY is trading at 99, how does a person who only holds U.S. dollars actually purchase the dollar?

For example, if someone in Japan decided to purchase a single USD for 99 yen, and then later sold their single USD for 100 yen, they will have profited one yen.

Now, how does this work for someone who doesn't originally own any yen, but wants to purchase USD?

I'm having trouble understanding what is going on when someone wants to long the USD against, say, the Japanese Yen, such as when they are longing the USD/JPY pair. What exactly is happening? How does such a trade work?

• You could use your USD100 to purchase USD100, taking advantage of the 1:1 USD:USD exchange rate? If you want to take advantage of the exchange rate between USD and another currency, you need to buy some of that other currency first. Why is this even a question? Aug 2, 2013 at 11:54
• @Jon If someone doesn't originally own any Yen, but wants to buy USD, they have a few options. A) Buy USD using whatever currency they do hold. B) Sell whatever currency they do have at the current Yen/currency-they-hold exchange rate and buy Yen, then use those Yen to purchase USD. Aug 2, 2013 at 12:07
• @Jon The first part of this answer may be helpful too. Aug 2, 2013 at 14:07
• @JohnBensin The answer you provided as well as the one you edited that is on the front page have answered my question, and I was actually right all along, I was just phrasing my question in a way that might not have been understandable.
– Jon
Aug 2, 2013 at 22:14
• @Jon Not a problem. If you have another question, you can always post a new question, or edit this one to rephrase your original thought more clearly. Aug 3, 2013 at 4:47

For instance, if the USD/JPY is trading at 99, how does a person who only holds U.S. dollars actually purchase the dollar?

I think this is a good question. I used to have this question myself once upon a time.

When you "buy" the USD/JPY, you're not converting your dollars to dollars. Even when you "buy" EUR/JPY, you're not converting dollars to euros.... what you're doing is borrowing yen and lending euros.

Rollover is the interest paid or earned for holding a currency spot position overnight. Each currency has an overnight interbank interest rate associated with it, and because forex is traded in pairs, every trade involves not only 2 different currencies but also two different interest rates. However, unlike what many traders think, foreign exchange rolls are not based on central bank rates. Instead, forex rolls are constructed using forward points which are mostly based on overnight interest rates at which banks borrow unsecured funds from other banks. After all, the foreign exchange market works over-the-counter. Market and spot trades need to be settled and rolled forward every day. If the interest rate on the currency you bought is higher than the interest rate of the currency you sold, you will earn a positive roll. If the interest rate on the currency you bought is lower than the interest rate on the currency you sold, then you will pay rollover.

Since interest is charged and paid, you don't buy or sell anything... you borrow and lend and the currency in your account is the collateral.

So it may be more correct to say when you "buy" the USD/JPY, you've borrow yen and lent dollars. More precisely, you've borrowed yen from an interbank, sold them for dollars, then lent the dollars to an interbank for an interest payment. The dollars in your account never move. Its just the collateral. To "buy" \$1000 of USD/JPY, you need only have \$20 in your account. \$30 for the EUR/JPY. Why bother to convert \$30 on such margin?

If you really wanted to convert your dollars to euros, you'd have to go to europe or find a bank that can make the exchange, or a private party willing to swap. Since you've taken possession of euros and haven't lent them out, you won't get paid an interest rate for holding the euros. You also won't get charged an interest rate for borrowing dollars, since you didn't borrow them, you owned them outright in the beginning.

Of course, if you wanted to find a US bank to loan you dollars, then fly to europe and convert your dollars to euros, then find someone looking to borrow euros,,, you could accomplish the same thing a forex account does by simply buying EUR/USD. In the meantime, you have nothing in your hand but an obligation to pay interest to the US bank and the expectation of an interest payment from the person who borrowed the euros from you. To close the trade, you'd have to demand full payment from the one who borrowed your euros, convert back to dollars, then pay the loan at the US bank.

• Thanks for a reply to the question. What do you mean by borrowing yen and lending euros? I understand that I might be borrowing yen from my broker, but I thought I am using that yen to now "purchase" USD in the case of USD/JPY or purchase euros in the case of EUR/JPY. Can you clarify what you mean by "lend"? Thanks.
– Jon
Aug 11, 2013 at 16:48
• @Jon If you borrow yen (from an interbank) to buy USD, you then lend the USD to an interbank (its not your choice, that's just how forex works). You have to pay an interest for the yen loan and you collect an interest for the USD loan. The only way to convert yen to USD would be to have some yen in the first place, like you said. Aug 11, 2013 at 17:11
• So what will actually cause the increase or decrease in the currency pair? If the USD/JPY goes down (which it has this past week), does that mean more people are lending YEN and borrowing USD? Would I actually be lending USD in this example (shorting) since I own the USD to begin with?
– Jon
Aug 12, 2013 at 0:22
• @Jon The conversion of yen to dollars and dollars to yen causes the increase and decrease. If the USD/JPY goes down, it means supply/demand for USD is going up and supply/demand for JPY is going down. Also, more than just forex traders drive currencies. There are other forces in play. Yeah, you would be lending USD in that example, but not because you have USD already. If you bought EUR/JPY, you'd be lending EUR. Aug 12, 2013 at 6:49

The currency market is the most liquid and mature securities market on the planet as a result of its relative age. To that end, brokerages have automated this trading process for their clients.

To long one's own currency vs another currency, one only need to enter the proper trade. In a forex account, the distinction of one's home currency is largely lost.

As with any currency, to long a currency thus short another, a trader simply borrows the shorted currency much like with a more commonly known short stock sale and simultaneously sells it to buy the long currency all while posting a margin in excess of the loan.

As with equities, the forex market has benefited significantly from electronic trading and algorithmic market makers with collapsing round lot sizes and spreads, typically 1/2 pip and lower for larger traders and specialized brokers/exchanges. Odd lot exchanges have arisen providing trading for any size below the current conventional round lot minimum of ~\$25,000, albeit for a higher minimum spread.

While one can use derivatives to trade forex, the most liquid trade is the spot market using the process described above. Because of the relative stability in the large currencies for the past few decades relative to the century before, margin rates for forex are the largest publicly available.

Indeed, a trader does pay interest on shorted currency while receiving interest on the longed currency, explaining the appeal of the so-called "carry trade", where a trader shorts a currency with lower borrowing costs to benefit from the higher interest rate of the longed currency.