Pre-trade analysis

What it means

A proposed stock trade has more dimensions than its quoted price. Before an order is placed, a pre-trade check examines its size, likely execution costs, available liquidity and relevant risks. For a basket, it also considers how the proposed lines fit together. This is an institutional execution discipline adapted to a private investor’s decision process—not a prediction of the stock’s return.

Pre-trade analysis uses estimates available before execution. Post-trade analysis instead measures what happened using actual fills. Neither can establish in advance the price at which an order will fill.

How it is calculated

There is no single universal pre-trade-analysis formula or score. A practical check combines several measures. For example, an order’s share of typical daily trading volume is:

Participation rate (%) = (Q / ADV) × 100

• Q is the proposed order size, in shares.
• ADV is average daily volume over a stated lookback period, in shares per trading day.

A simple estimated execution-cost breakdown is:

Estimated cost (US$) = Q × P × (spread cost (bps) + market impact (bps)) / 10,000

• P is the reference price, in US$ per share; Q × P is the order’s reference value in US$.
• Spread cost is the estimated cost of crossing the bid-ask spread, measured in basis points of order value. It is not necessarily the full quoted spread; a midpoint-to-quote estimate, for example, uses half the quoted spread.
• Market impact is the estimated price effect of executing the order, also in basis points of order value. One basis point is 0.01%.

These are illustrations, not a complete model. A fuller assessment may account for commissions, order conditions, volatility, data quality and basket concentration. Avoid adding cost components twice if an impact estimate already includes a spread component.

Worked example

Suppose, hypothetically, a proposed buy order is 1,000 shares at a reference price of US$50. Assume the stock’s ADV is 100,000 shares per trading day, estimated spread cost is 5 basis points, and estimated market impact is 10 basis points.

1. Reference order value: 1,000 × US$50 = US$50,000.
2. Participation rate: (1,000 / 100,000) × 100 = 1% of ADV.
3. Combined estimated cost: 5 + 10 = 15 basis points, or 0.15% of reference value.
4. Estimated dollar cost: US$50,000 × 15 / 10,000 = US$75.

The US$75 is a hypothetical pre-trade estimate, not a commission figure, guaranteed fill cost or expected profit or loss. Actual execution can differ as quotes, volume and market conditions change.

Why it matters before you trade

An order that looks small in dollars can still be large relative to a stock’s usual volume. A wider spread or greater estimated impact can make execution more costly; volatile prices and concentrated basket exposures add different risks. Checking these separately helps distinguish the question of what the stock might do from what placing this particular order could involve.

Execution conditions matter too: order type, price limits, timing and partial-fill rules can change the trade-off between the chance of a fill and control over its price. A pre-trade estimate informs that trade-off but cannot guarantee an outcome.

How PreTrAIde uses it

PreTrAIde is AI pre-trade analysis software for stocks, not a broker or investment adviser. A user builds a basket with a buy or sell side, quantity and execution conditions for each stock. Before any order is placed, its PreTrade analysis returns a GO, NO-GO or MODIFY verdict for the basket and each line, alongside a model-estimated success probability, risk assessment, suggested execution strategy and plain-language reasoning. These verdicts support a decision; they are not recommendations.

Its quantitative layer estimates spread, participation in daily volume, market impact, daily volatility and one-day 95% value at risk, among other measures. AI agents reason from quantitative scores, news and analyst ratings; guardrails can correct contradictory output in a conservative direction. PreTrAIde never receives, transmits or executes an order. Users place any trades themselves through their own broker.

Common mistakes

• Treating an estimate as a fill price. Costs and liquidity can change before and during execution.
• Confusing execution cost with investment return. A cost estimate says nothing certain about the stock’s subsequent performance.
• Ignoring units or double-counting costs. Share volume, dollar value and basis points are different measures; check what each model’s impact estimate includes.
• Assuming a verdict is an instruction. PreTrAIde’s GO, NO-GO and MODIFY labels are decision support, not orders or investment advice.