Liquidity

How it's measured

No single number captures it. Traders combine several:

• Volume and dollar volume: shares traded, and shares × price.
• Bid-ask spread: the cost of crossing from buyer to seller.
• Depth: how much size rests near the current price in the order book.
• Impact: how far price moves for a given order size.

Why it matters

Liquidity decides how close your fills are to the prices on the chart. In thin markets, small orders move price, stops fill far from their levels, and slippage eats into any edge. Liquidity also changes with the clock: premarket and after-hours are usually much thinner than the regular session, and liquidity can vanish around news or trading halts.

Example

For example, two hypothetical stocks both trade at $5.00. Stock A trades 3 million shares a day with a one-cent spread; stock B trades 80,000 shares with a five-cent spread. Buying 2,000 shares and selling them straight back costs about $20 in spread on A and about $100 on B, before any price impact. On B, an order that size may also move the price.

Common mistakes

• Judging liquidity by share price or company size alone.
• Using full-day volume to judge premarket conditions.
• Sizing a position larger than the book can absorb.

How PatternX uses it

Every chart-pattern signal must pass universal market filters, including a liquidity score of at least 30, a spread no wider than 0.25%, order-book imbalance against the trade no worse than −0.5 and, for crypto, at least $3M of 24-hour volume. Liquidity also counts toward the PatternX Score with a weight of .08. Pattern backtests use a neutral market context, so these filters are effectively off there. Momentum Lab applies its own defaults: at least 50,000 shares of premarket volume (100,000 for Momentum Reversal), $250,000 of premarket dollar volume and a maximum spread of 1% of mid.