Trading journal

What it means

A useful journal keeps the decision made before a trade separate from the execution and outcome recorded afterward. It might contain the stock, side, intended quantity, planned execution conditions, reason for the decision, actual fill prices, fees and a later valuation. Skipped trades can be recorded too: they show what was considered without being executed.

A journal can be a spreadsheet, notebook or software record. Its purpose is to make a decision reviewable. A pre-trade note captures what was known at the time; a post-trade entry captures what happened. The later price movement alone cannot tell you whether the original decision process or execution was sound.

How it is calculated

A trading journal is a record, not a metric with one standard formula. One simple measure for a completed, long stock trade is its net dollar result:

Net result (US$) = Q × (P_exit − P_entry) − C

• Q is the number of shares bought and later sold, in shares.
• P_entry is the actual purchase fill price, in US$ per share.
• P_exit is the actual sale fill price, in US$ per share.
• C is the total recorded costs for both transactions, in US$; avoid counting a cost twice if it is already reflected in a fill price.

This formula assumes the same number of shares is bought and sold. For partial fills, multiple fills or an open position, keep each execution and its quantity in the record. An unrealized change in value is not a completed trade result. A journal may also track execution cost against a specified reference price, but that is a different measure from the net result.

Worked example

The following numbers are hypothetical. Suppose an investor plans to buy 100 shares, noting an intended maximum price of US$50.00 per share.

1. The journal records the plan before execution: 100 shares, a US$50.00 price limit and the reason the trade is being considered.
2. The broker fills 60 shares at US$49.80 and the remaining 40 at US$49.90. The investor records both fills. The quantity-weighted entry price is (60 × US$49.80 + 40 × US$49.90) ÷ 100 = US$49.84 per share.
3. Later, all 100 shares are sold at a hypothetical US$51.00 per share. Recorded transaction costs across the purchase and sale total US$4.00.
4. The completed net result is 100 × (US$51.00 − US$49.84) − US$4.00 = US$112.00.

The US$112.00 result describes this hypothetical completed trade; it does not establish that the earlier decision was well founded. The journal can separately compare the actual purchase fills with the original price limit and explain any change in the plan.

Why it matters before you trade

A journal starts being useful before the first fill. Writing down the intended side, quantity, execution conditions and risks creates a dated point of comparison for the eventual outcome. It also helps distinguish a skipped trade from one that was attempted but only partially filled.

That separation matters when reviewing patterns. A difference between the planned and actual quantity may reflect execution; a difference between the expected and realized outcome may reflect market movement. Neither should automatically be attributed to a single cause. Consistent fields make reviews more comparable, while notes preserve context that numbers cannot capture.

How PreTrAIde uses it

PreTrAIde provides pre-trade analysis for a stock basket before an order is placed. Its GO, NO-GO or MODIFY verdict, success probability, risk assessment, suggested execution strategy and reasoning are decision support, not recommendations or guaranteed outcomes. Users place trades themselves through their own brokers.

With PreTrAIde Memory, users can log what they actually did: executed, partially executed or skipped a trade, and their real fill prices. PreTrAIde measures the outcome from market data and builds a per-account memory that personalizes later analyses in the AI layer only; quantitative scores remain identical. Users can pause or erase that memory. This logging supports comparison between a pre-trade analysis and later events; it is not a broker execution record.

Common mistakes

• Recording only completed trades. Skipped and partially executed trades provide context for reviewing decisions.
• Replacing planned prices with fill prices. Keep both so the original plan remains visible.
• Ignoring costs or partial fills. Use actual quantities and prices when calculating a result.
• Treating profit as proof of good process. One outcome does not isolate decision quality from execution and market movement.
• Treating a model estimate as an outcome. A pre-trade success probability is not a realized return or a guarantee.