Currency Pair: One Priced in Another
A currency pair is one currency priced in another, quoted as a base currency measured in units of a quote currency. Buying the pair buys the base and sells the quote at the same time, so every forex position is a bet on the two together rather than on either alone.
How it works
A currency pair is one currency measured in another. The first named is the base, the second the quote, and the price is how many units of the quote buy one unit of the base.
The first currency is what you are buying. Forex, or foreign exchange, deals only in these ratios: buying the pair buys the base and sells the quote in one action.
So a fall is a rise in the other one. No currency goes down on its own; every quote is a ratio, and a falling ratio means the second currency strengthened.
Which is the part most people skip. You cannot be long a currency alone. Every position is relative, so a view on one currency is incomplete until you pick its counterpart.
The conventions attached to it
The smallest step is a convention, not a law. A pip is the last decimal place of a conventional quote — the fourth for most pairs, the second for Japanese yen pairs.
A handful of pairs carry almost all the volume. A major has the United States dollar on one side and enough liquidity to keep quotes tight all day.
And a cross is two pairs divided by each other. A pair with no dollar in it is priced from the two behind it, so it inherits the bid-ask spread of both. Exotics are wider still: fewer dealers quote them.
Holding one overnight pays or charges interest. At the daily rollover the position is financed at the interest-rate difference between the two currencies — the higher-yielding side credits, the other debits. One video in the corpus covers it, at 1,085 views.
There is no central exchange, so volume is an estimate. Spot forex is dealt across a network of banks, brokers and market makers, so the volume your platform draws is your broker’s own flow.
In practice
Liquidity follows the clock. The london session and new york session overlap has the tightest spreads and widest ranges; the asian session is quieter. Trading sessions measures it.
On a daily chart the session effects disappear. A daily bar holds every session at once, so an intraday rule and a daily rule answer different questions.
The only real gap arrives on a Sunday open. Trading runs Sunday evening to Friday evening with no daily close, so an opening gap carries a whole weekend of news.
And the stop is sized in pips, not in currency. A stop loss sits at a level; what it costs depends on the lot size attached and the leverage behind it. Seventeen videos cover lot size, median 74,124 views.
Every round trip costs 2% of a bar. On this site’s shared 576-bar history a round-trip cost of 0.0098 price units is 2% of the median bar’s range of 0.493.
Your broker’s price is one of several versions. Two feeds can print different highs for the same hour, so a level read off one is not exactly another’s.
Choosing which pair to say it in
A view about one currency still has to be expressed against another, and the counterpart you pick decides how much of the result has nothing to do with your reasoning.
So pick the quiet side. If the view is that a currency weakens, express it against the one with the least of its own story running — no policy meeting due, no commodity it tracks in the headlines. Whatever happens on the other leg is noise you did not choose.
If the view is genuinely about both, say so out loud. “This one is strong and that one is weak” is a stronger claim than either half, and a cross rather than a major is the honest instrument for it.
And check the pair can carry the view. A thesis measured in weeks does not belong on an exotic whose spread takes most of the move first.
What a currency pair is not
It is not a single asset. It is a ratio, and both sides of it move independently.
It is not a stock with a ticker. Nothing is issued, and there is no earnings date.
It is not quoted identically everywhere. Your broker’s feed is one version of the price.
And it is not free to hold. Past the rollover, the rate difference is charged or credited nightly.
When it fails
You formed a view on one currency only
Half a thesis is still a whole position. The leg you never thought about carries the same weight as the one you did.
The other side had the news
A pair can move for reasons that have nothing to do with your currency. Right about the base and wrong about the quote reads the same as simply wrong.
It was a range, and the spread was most of the move
In a range the spread is a bigger share of the move. On this shared history the round trip exceeds a tenth of a bar’s range on 15 of the 576 bars, and a trading range is where those bars gather.
You expected a run and got two bars
Direction runs on that series average 2.01 bars across 286 runs, with a longest of 11. Continuation is the exception, and sizing for the exception is how an edge gets spent.
You traded it in its dead session
Bar ranges run from 0.17 at the tenth percentile to 1.101 at the ninetieth, a ratio of 6.5. The pair does not change overnight — the number of people trading it does, and the cost stays where it was.
The original data
Three videos in the whole corpus explain what a currency pair is. A scan of the 31,760 titles in
research/search-study-corpus.jsonl, recorded in research/broker-coverage.json, finds 1,649 with
“forex” in them, at a median of 8,379 views across 724 channels and a maximum of 7,449,304. Those
three have a median of 105,916 — more than twelve times the forex median.
The market is saturated with trading content and nearly empty of explanation.
research/series-measurements.json, measured by site/measure_series.py, prices the other half: the
round trip is 45% of the smallest bar here, so on quiet bars the spread is most of the available move.
So before entering, write down what you believe about both currencies — the position contains a view
on each whether or not you formed one.
Related
Forex is the market these pairs trade in, and what having no exchange changes.
Trading sessions is why the same pair behaves differently by the hour.
And the bid-ask spread is the cost that decides whether the move was ever worth taking.
The habit that took me longest to build here was holding two ideas at once. I would decide one currency looked weak, pick a pair, and then be surprised by the other side doing something I had never considered. Now I make myself say both halves out loud before I click anything, and if the second half comes out blank I know I have only half a trade. It is not a clever technique — it is refusing to pretend a ratio is a single thing.
— Michael Whitman
This page is educational, not financial advice. Test every idea on your own charts before risking money.