Variables required to calculate position size based on % risk?

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I'm a little confused about something.  I'm still learning to code so I haven't actually attempted this yet but I have previously done it with excel.  I just need some clarification on something.  Which variables are part of the equation to calculate position size?

Suppose my account is in USD, then any pair that ends with USD is pretty straightforward.  I know I need my account balance or equity, the distance to the stop loss and the amount I want to risk.  But if I want to calculate my position size say for example, GBP/CHF then I need to also use the current price for USD/CHF, don't I?

I can't simply calculate the position size the same was as if I were calculating for GBP/USD because the lots will be in CHF.  So, is there a way to lookup the current price for another pair?  

...or am I misunderstanding this somewhere?

 
  1. Never risk more than a small percentage of your trading funds, certainly less than 2% per trade, 6% total.

    Risk depends on your initial stop loss, lot size, and the value of the pair. It does not depend on margin and leverage. No SL means you have infinite risk.

    1. You place the stop where it needs to be — where the reason for the trade is no longer valid. E.g. trading a support bounce the stop goes below the support.
    2. AccountBalance * percent/100 = RISK = OrderLots * (|OrderOpenPrice - OrderStopLoss| * DeltaPerLot + CommissionPerLot) (Note OOP-OSL includes the spread, and DeltaPerLot is usually around $10/pip but it takes account of the exchange rates of the pair vs. your account currency.)
    3. Do NOT use TickValue by itself - DeltaPerLot and verify that MODE_TICKVALUE is returning a value in your deposit currency, as promised by the documentation, or whether it is returning a value in the instrument's base currency.
                MODE_TICKVALUE is not reliable on non-fx instruments with many brokers - MQL4 programming forum 2017.10.10
                Is there an universal solution for Tick value? - Currency Pairs - General - MQL5 programming forum 2018.02.11
                Lot value calculation off by a factor of 100 - MQL5 programming forum 2019.07.19
    4. You must normalize lots properly and check against min and max.
    5. You must also check FreeMargin to avoid stop out

    Most pairs are worth about $10 per PIP. A $5 risk with a (very small) 5 PIP SL is $5/$10/5 or 0.1 Lots maximum.

  2. Search for a GUI/Trade Assistant EA like mine (for MT4): 'Money Manager Graphic Tool' indicator by 'takycard' - Risk Management - Articles, Library comments - MQL5 programming forum - Page 6 #55

  3. dasilvja:   I need to also use the current price for USD/CHF, don't I? So, is there a way to lookup the current price for another pair? ...or am I misunderstanding this somewhere?
    The value of the pair/tick is in account currency. You don't need to do the conversion yourself.

  4. Or course there is. Perhaps you should read the manual.
              Timeseries and Indicators Access - Reference on algorithmic/automated trading language for MetaTrader 5
              Timeseries and Indicators Access - MQL4 Reference

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