DECIDE · CALCULATE · EXPLAIN

Forex Decision Lab

Practise ten decisions that a formula alone cannot make for you. Choose a response, work out the number, inspect the consequence and compare your reasoning with a worked explanation.

Hypothetical practice. All cases use invented inputs, and answers are processed in your browser. A correct answer solves the stated task; it does not establish readiness to risk money. Optional progress saving belongs to this browser, not to a verified student record. Site privacy policy.

The interactive cases are loading. If they do not appear, reload the page with JavaScript enabled. The case list and methodology remain available below.

Ten situations to work through

Start with a case related to your current lesson, or follow the sequence. Worked examples require JavaScript; existing calculator and lesson links below remain available. The links below select a case when the interactive module is available.

  1. JPY position on a euro accountConvert pip value in the right direction and size the position from a fixed risk budget.
  2. When execution costs consume the edgeConnect spread, commission and slippage with gross and net expectancy.
  3. Three positions, one common currencySeparate currency exposure from the sum of individual stop-loss budgets.
  4. A positive backtest and an uncomfortable pathInterpret trade order, drawdown and the limits of resampling.
  5. A journal with misleading recordsCheck units, duplicate records and the boundary between plans and completed trades.
  6. Collateral is not a loss budgetCompare required margin with the amount a price move can lose.
  7. The stop price and the fill priceCalculate what an assumed adverse fill does to the planned loss.
  8. Recovering after a drawdownUse the smaller remaining capital as the denominator for recovery.
  9. Two exits from one positionWeight partial outcomes consistently and count each cost once.
  10. The result after the rules are frozenDistinguish a selected historical result from a separate evaluation sample.

How to use the lab

  1. Decision: read the situation and select the response that fits the information provided. Compare the feedback with your reasoning.
  2. Calculation: enter a number in the requested unit. Check decimal places, currency-conversion direction and the base used for percentages.
  3. Consequence: inspect the result of the scenario under its stated assumptions. A model consequence is not a prediction of a live outcome.
  4. Explanation: follow the arithmetic and the limits of the example. Open the linked tool to explore another set of inputs.

A case has one marked decision and one numeric target within an explicitly defined model. Numeric checking uses the case's stated tolerance; rounding is part of the explanation where it matters. Real situations may contain missing or conflicting information that these exercises deliberately hold fixed.

The examples distinguish planned risk, required margin, realised P&L, gross and net costs, and descriptive sample statistics. The data-quality and testing cases concern the supplied records and assumptions; they do not validate a strategy or certify a trader. Repeating a known case can test memory as well as understanding.

Version 1.0.0. Use the worked steps to challenge a result. If you find inconsistent inputs, units or arithmetic, include the case title and your calculation in a message through the contact page.

Position size · Execution costs · Portfolio exposure · Journal analyzer · Strategy resilience

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Jarosław Wasiński

Editor-in-chief, ForexMechanics.com • Macro & FX analyst

Independent analyst and practitioner with over 20 years of experience in financial markets. Actively involved in Forex since 2007, with a focus on fundamental analysis, OTC market structure, and disciplined capital risk management.

  • Creator and editor-in-chief of MyBank.pl, providing reliable financial education since 2004.
  • Author of hundreds of in-depth market commentaries, structural analyses, and educational materials for traders and investors.
  • Advocate for market transparency, promoting education grounded in hard data and institutional reports (BIS, ESMA, CFTC).

All content is educational and informational only – it does not constitute investment advice or a recommendation. Remember: leveraged trading (Forex/CFD) carries a high risk of rapid capital loss.