Introduction
Position sizing determines how many shares, contracts, lots, or units you can trade while keeping the planned loss within a fixed account-risk limit. Correct sizing allows the stop to reflect market structure instead of forcing every trade into the same quantity.
This guide explains the position-sizing process and how to journal it accurately.
A useful review process should explain not only what happened, but also whether the trade followed a repeatable plan. That distinction is essential because one profitable or losing outcome can be misleading. The same structure should be applied consistently so that similar trades can later be compared with real evidence.
Why This Matters
Many traders react emotionally to individual outcomes. They change strategy after a few losses, increase risk after a winning streak, or blame the market for problems caused by execution. A structured journal reduces this confusion by separating strategy performance, risk, execution, and psychology.
The objective is not to remove every losing trade. Losses are part of any probabilistic strategy. The objective is to reduce avoidable losses, improve repeatable decisions, and understand whether the current results are normal for the strategy.
Step 1: Choose the account-risk amount
Start with account equity and the permitted risk percentage. For a ₹500,000 account risking 0.5%, the planned risk is ₹2,500.
Use the same equity definition consistently. If open positions or withdrawals affect the base, record which value was used.
During the review, write down the evidence that supports your conclusion. Avoid changing a rule because one chart looks convincing after the outcome is known. Compare similar trades and keep the original plan unchanged so hindsight does not rewrite the decision.
Step 2: Define the technical stop
Place the stop where the trade thesis becomes invalid according to the strategy. Do not choose the quantity first and move the stop to fit the desired position.
The stop may be based on swing structure, volatility, range boundary, or another tested rule. Record the exact reason.
During the review, write down the evidence that supports your conclusion. Avoid changing a rule because one chart looks convincing after the outcome is known. Compare similar trades and keep the original plan unchanged so hindsight does not rewrite the decision.
Step 3: Calculate loss per unit
Subtract the stop price from the entry price and adjust for instrument specifications.
For shares, loss per unit is usually the price difference. For forex, futures, options, and CFDs, include pip value, tick value, contract multiplier, lot size, and currency conversion.
During the review, write down the evidence that supports your conclusion. Avoid changing a rule because one chart looks convincing after the outcome is known. Compare similar trades and keep the original plan unchanged so hindsight does not rewrite the decision.
Step 4: Calculate the position size
Use the simplified formula:
`Position size = Risk amount ÷ Loss per unit`
If planned risk is ₹2,500 and loss per share is ₹25, the position size is 100 shares. Round down when the instrument does not allow the exact size.
During the review, write down the evidence that supports your conclusion. Avoid changing a rule because one chart looks convincing after the outcome is known. Compare similar trades and keep the original plan unchanged so hindsight does not rewrite the decision.
Step 5: Include fees, slippage, and gap allowance
If costs are material, reserve part of the risk amount for commission, spread, and expected slippage.
For overnight or highly volatile trades, consider whether the stop can be filled beyond the planned level. The final size may need an additional safety buffer.
During the review, write down the evidence that supports your conclusion. Avoid changing a rule because one chart looks convincing after the outcome is known. Compare similar trades and keep the original plan unchanged so hindsight does not rewrite the decision.
Step 6: Check portfolio and leverage limits
Confirm that the required margin, notional exposure, leverage, and total open risk remain within account rules.
A mathematically correct single-trade size can still create excessive account exposure when combined with correlated positions.
During the review, write down the evidence that supports your conclusion. Avoid changing a rule because one chart looks convincing after the outcome is known. Compare similar trades and keep the original plan unchanged so hindsight does not rewrite the decision.
Step 7: Record planned and actual size
Store the calculated quantity, final order quantity, actual fill, stop, and final risk. Explain any difference caused by rounding, liquidity, or broker limits.
Review sizing errors weekly. Repeated differences may justify an automated calculator or order-entry warning.
During the review, write down the evidence that supports your conclusion. Avoid changing a rule because one chart looks convincing after the outcome is known. Compare similar trades and keep the original plan unchanged so hindsight does not rewrite the decision.
Common Beginner Mistakes
Choosing quantity before the stop
This reverses the correct risk process.
Ignoring contract specifications
Different instruments use different value calculations.
Rounding up
This can exceed the planned risk.
Ignoring fees and slippage
Actual loss may be larger.
Forgetting correlated exposure
Portfolio risk may become excessive.
Practical Tips
- Use an automated calculator: Reduce manual arithmetic errors.
- Round down: Protect the risk limit.
- Save the formula inputs: Make the calculation auditable.
- Use stop-based sizing: Let invalidation determine quantity.
- Review actual versus planned loss: Improve assumptions over time.
How Trade Diary Helps
Trade Diary can store entry, stop, quantity, planned risk, and actual result together. This makes sizing errors visible and supports average-risk and maximum-risk analysis.
Trade Diary keeps the strategy, risk, trade rules, screenshots, notes, and final result connected to the same record. This reduces the need to maintain separate spreadsheets and makes it easier to compare groups of trades by strategy, market, date, and compliance.
The platform can also help you review whether losses came from normal strategy variance or repeated rule-breaking. Calendar views, risk analytics, strategy filters, and performance summaries make it easier to detect patterns that are difficult to notice from individual trades.
Frequently Asked Questions
Risk amount divided by loss per unit, adjusted for contract specifications.
Choose one consistent base that fits your risk plan.
Use stop distance in pips, pip value, lot size, and account currency conversion.
Skip the trade or use a smaller instrument when possible.
Leverage affects margin and exposure, but stop distance and position size determine planned loss.
Final Checklist
Before completing the review, confirm that you have:
- Preserved the original trade plan.
- Recorded planned and actual risk separately.
- Checked whether the setup matched a documented strategy.
- Reviewed market context and execution.
- Marked all broken rules honestly.
- Calculated the financial impact where possible.
- Written one specific lesson.
- Selected one measurable next action.
- Avoided changing the strategy from a small sample.
Conclusion
Position sizing should begin with account risk and strategy invalidation. Calculate the loss per unit, adjust for costs and instrument rules, round conservatively, and record both planned and actual exposure.
A journal becomes more valuable when every trade is reviewed with the same standards. Use objective language, compare similar trades, and convert findings into practical actions rather than emotional reactions.