The MyFxBook Position Size Calculator includes about 40 currency pairs in its drop-down menu, which is more than most calculators offer. But, no calculator can list all the possible currency pairs, because the total number of possible pairs is surprisingly large. More on that in the second portion of this post.
So, judgments have to be made by the developers of online forex calculators, regarding which pairs to include and which ones to exclude.
Generally, the pairs included in these calculators are the most heavily traded pairs, based on worldwide trading volume. Unfortunately for you, the GBP/HKD pair that you want to trade isn’t one of the most heavily traded pairs, and therefore isn’t included in the MyFxBook Position Size Calculator (or in any other position size calculator that I’m familiar with).
The only solution I can suggest is manually calculating the GBP/HKD position size.
HERE you’ll find instructions for doing the calculation by hand.
Here is some information regarding individual currencies and currency pairs. This information is not directly related to your question, but you might be interested in it, nevertheless.
• The 8 major currencies (USD, EUR, JPY, GBP, AUD, CAD, CHF, and NZD) can be combined to form 28 currency pairs.
Drop-down menus in position size calculators typically include these 28 pairs, but no others. Good examples are the Babypips Position Size Calculator and the EarnForex Position Size Calculator.
• The second tier of currencies, typically referred to as minor currencies, consists of 13 additional currencies. The HKD is among this group of 13. The complete list of minor currencies is: CNY, SEK, MXN, SGD, HKD, NOK, KRW, TRY, INR, RUB, BRL, ZAR, and DKK.
Together, the major currencies plus the minor currencies total 21 individual currencies, which can be combined into 210 currency pairs. The GBP/HKD pair that you are interested in is one of those 210 pairs.
Some online forex tools (the MyFxBook Position Size Calculator, for example) add some of the minor USD pairs to the basic menu of 28 pairs. These minor USD pairs might include the USD/HKD, but not the GBP/HKD.
• The third tier of currencies is typically referred to as exotic currencies, and consists of all the rest of the world’s currencies – many of which you probably have never heard of.
The total number of currencies (majors + minors + exotics) is around 168 individual currencies. (Not everyone agrees with that count. Wikipedia lists 180 “circulating” currencies. And I’ve seen other totals listed, as well.)
If we use the figure of 168 currencies, we find that they can be combined to form 14,028 currency pairs. Clearly, that total number is unmanageable in forex tools such as position size calculators – which is why only the most heavily traded pairs appear in those tools.
• The Bank for International Settlements (BIS) lists 35 individual currencies in their Triennial Central Bank Survey. These are the 35 most heavily traded currencies worldwide. Trading in these 35 currencies accounts for 91% of world forex trading volume, according to THE MOST RECENT SURVEY. Those 35 currencies can be combined into 595 currency pairs.
• If you are interested, here is the formula for determining the number of pairs which can be formed from a given number of currencies:
For x-number of individual currencies, the number, N, of possible currency pairs is: N = (x-1) * (x/2)
So, for the world total of 168 currencies, this formula tells us that the number of currency pairs is:
N = (168-1) * (168/2) = (167) * (84) = 14,028 currency pairs.