LotSizeCalculator

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1. Open MetaTrader 5.

2. From the menu: File -> Open Data Folder.

3. Navigate to:  MQL5\Experts\

4. Create a new sub-folder named:  LotSizeCalculator

5. Copy ALL of these files into that folder:

       - LotSizeCalculator.mq5

       - Defs.mqh

       - RiskCalc.mqh

       - CommissionDetector.mqh

       - ChartLines.mqh

       - Panel.mqh

6. In MT5, open the MetaEditor (F4 in MT5, or open MetaEditor.exe).

7. In the Navigator panel, find:

       Experts -> LotSizeCalculator -> LotSizeCalculator.mq5

8. Right-click the file -> Compile (or press F7).

   The file should compile with 0 errors / 0 warnings.

9. Back in MT5, in the Navigator under Experts you will now see

   "LotSizeCalculator". Drag it onto a chart.

10. In the dialog that appears:

    - "Common" tab: tick "Allow algo trading"

    - "Inputs" tab: review settings (defaults are fine for first run)

    - Click OK.

The panel will appear in the top-left of the chart.

USAGE

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Header (top of panel)

    Symbol     - the chart's symbol

    Balance    - account balance

    Equity     - account equity

    Spread     - live spread in pips (auto-detected per tick)

    Comm/lot   - commission per 1 lot, round trip:

                 - "auto" if detected from your trade history

                 - "manual" if using the InpManualCommission input

                 Click [Re-scan] to retry history detection.

Risk

    Mode toggle:  [%]  =  percent of balance

                  [$]  =  fixed money

    Edit field    your number

    Below shows the resolved money amount.

Order  (execution type)

    Mode toggle:  [Mkt]   market order at current price (default)

                  [Pend]  pending order (Limit / Stop)

    Entry field   in Pending mode, type the trigger price (or drag the

                  blue Entry line on the chart). In Market mode it just

                  shows "(market)".

    Below shows the resolved pending type, e.g. "= Buy Limit @ 1.2345".

    The exact type is chosen automatically from your Entry vs. the

    current market and the direction:

        BUY :  Entry below Ask -> Buy Limit,  Entry above Ask -> Buy Stop

        SELL:  Entry above Bid -> Sell Limit, Entry below Bid -> Sell Stop

    In Pending mode, SL/TP pip distances and the lot are measured from

    your Entry line (not the live price), so the risk is correct for the

    price the order will actually trigger at. Pending orders are GTC

    (good till cancelled). An Entry too close to the market (within the

    broker's stops level) is rejected with a message.

SL

    Mode toggle:  [Pips]   distance in pips from entry

                  [Price]  absolute SL price

    The lot is sized so that the actual loss when SL is hit equals

    your Risk amount, INCLUDING spread and commission.

TP

    Mode toggle:  [Pips]   distance in pips

                  [Price]  absolute TP price

                  [R:R]    take-profit as a multiple of SL distance

Results (live)

    Lot Size      calculated lot, rounded to broker's lot step

    Real Risk     real money loss when SL hits, includes commission

    Real Reward   real money gain when TP hits, minus commission

Action

    [BUY]   in Market mode: market buy at Ask. In Pending mode: places

            a Buy Limit or Buy Stop at your Entry. SL/TP are placed so

            the SL distance from entry equals your configured pips.

    [SELL]  mirror of BUY (Sell / Sell Limit / Sell Stop).

    Direction is detected automatically from where the SL line sits:

       SL line BELOW current price → BUY setup  → BUY button highlighted

       SL line ABOVE current price → SELL setup → SELL button highlighted

    The inactive direction's button is dimmed but still works (it will

    flip the line to the other side and execute the opposite trade).

Chart lines (when "Show ... lines" is on)

    - Solid blue   = Entry. Market mode: follows live Ask. Pending mode:

                     draggable, sets your limit/stop trigger price.

    - Dashed red   = SL (the absolute SL price you chose)

    - Dashed green = TP (the absolute TP price; auto-flips with direction

                     in R:R / Pips modes)

    The SL line is the SOURCE OF TRUTH. Drag it freely:

       - Drag BELOW current price → BUY setup. TP is placed ABOVE Ask

         (R:R / Pips modes auto-position TP on the other side of entry).

       - Drag ABOVE current price → SELL setup. TP is placed BELOW Bid.

    The line stays exactly where you put it; it does NOT snap back. Each

    tick the panel measures the live pip distance from the relevant

    entry (Ask for BUY, Bid for SELL) to your SL line, and recomputes

    the lot size so the realized loss when SL is hit equals your Risk

    amount. As price drifts, the lot adjusts; the line stays anchored.

    Typing a value into the SL or TP field does the inverse: it moves

    the line to that distance (pips, on the side matching the current

    direction) or to that absolute price. Pressing Enter commits the

    move; clicking BUY or SELL also commits any unsubmitted edit.

NOTES

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- Before sending an order the EA checks: AutoTrading is on, Algo

  Trading is allowed for the EA, the account/broker permits trading,

  the symbol is tradable, and there is enough free margin for the

  lot. If any check fails, the status line explains why and NO order

  is sent.

- Auto-commission requires you to have at least one closed trade on

  this symbol within the InpCommLookbackDays window. If none, the

  EA falls back to InpManualCommission.

- Lot sizing formula:

       Lot = Risk_Money / (SL_pips * PipValuePerLot + Commission_RT)

- SL price for BUY = Ask - SL_pips, for SELL = Bid + SL_pips. This

  makes the SL distance from your entry equal exactly to the pips

  value displayed, so the realized loss matches the calculation.

- One EA per chart. Different charts can have different settings.