Position sizing is arithmetic, not vibes

Описание и применение

Инструмент Position Sizer автоматически рассчитывает размер позиции, учитывая цену входа, стоп‑лосс и бюджет риска, и предупреждает, если минимальный лот брокера не позволяет соблюсти заданный риск.

Задача

Trade plans often fail because position size is chosen by feel and stop is priced after the fact, leading to unintentional risk exceeding the budget.

Результат

The Position Sizer tool eliminates the common mistake of over‑risking by providing precise position sizes and alerting when broker minimum lot sizes prevent compliance with the risk budget.

Рабочий процесс

• 1. Input instrument, entry price, stop price, and maximum loss budget into the Position Sizer tool.
• 2. The tool calculates risk per unit as |entry – stop| × contract value per unit.
• 3. It computes position size as risk budget ÷ risk per unit, rounding down to the nearest allowable lot size.
• 4. If the calculated size is below the broker’s minimum lot, the tool outputs a warning: "NO COMPLIANT SIZE EXISTS FOR THIS PLAN" and shows the minimum lot risk.
• 5. The trader reviews the result or warning before placing the trade.
• 6. If a compliant size exists, the trader places the trade with the calculated position size; otherwise, the trader adjusts the stop, increases the budget, or abandons the trade.

Доказательства

Position sizing is the one part of trading that is pure arithmetic. It deserves to be done like arithmetic.

Источник

The contract value is where people slip. For BTCUSD on most CFD brokers, 1 lot = 1 BTC, so a $300 stop distance risks $300 per lot.

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The minimum lot can break you before the market does.

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MIN-LOT WARNING — NO COMPLIANT SIZE EXISTS FOR THIS PLAN Minimum lot 0.01 risks $8.00 — MORE than your $5.00 cap.

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I turned the checklist into a small tool: a Claude skill file plus a plain-Python program (standard library only, no installs, works offline).

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