A problem with mathematical calculation

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Hello! Faced with a problem... I wrote the calculation of the lot relative to the stop loss:

 double lot= NormalizeDouble ((risk_money/(dist/ _Point ))/tick_value, 2 );

where risk_money=$200;

dist=0.00053;

tick_value=1.0;

Everything worked, but when the stop loss was triggered, it turned out to be -220.55.

When I tried to do the reverse calculation:

 double dist= NormalizeDouble (( 220.55 /(tick_value*lot))* _Point , _Digits );

then i got dist=0.00059...

that is, dist from the first formula is not equal to dist from the second formula...

I understand that it has something to do with the division operator, but how do I solve this?

 

Risk depends on your initial stop loss, lot size, and the value of the symbol. It does not depend on margin or leverage. No SL means you have infinite risk (on leveraged symbols). Never risk more than a small percentage of your trading funds, certainly less than 2% per trade, 6% total.

  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 You place the stop where it needs to be — where the reason for the trade is no longer valid.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. Then you compute your lot size.

  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)
              Is there an universal solution for Tick value? - Currency Pairs - General - MQL5 programming forum (2018)
              Lot value calculation off by a factor of 100 - MQL5 programming forum (2019)

  4. You must normalize lots properly and check against min and max.

  5. You must also check Free Margin to avoid stop out

  6. For MT5, see 'Money Fixed Risk' - MQL5 Code Base (2017)

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.

 
I found the reason! The fact is that the broker's commission is not taken into account in the calculation of the lot, hence the discrepancy... Hence the next question: is it possible to somehow determine the broker's commission before opening the order?
 
Maksim Neimerik #:  is it possible to somehow determine the broker's commission before opening the order?

No. Ask them.

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