The ease with which a security can be bought or sold in the market without significantly affecting its price.
Liquidity refers to how quickly and efficiently a security can be converted to cash at a price close to its true market value. A highly liquid stock can absorb large buy or sell orders with minimal price impact, while an illiquid stock may see its price move sharply even on small trades.
Liquidity is measured through several indicators: trading volume (number of shares traded daily), bid-ask spread (the difference between the highest buy price and lowest sell price in the Order Book), and impact cost (the price change caused by executing a standard order size). On the NSE, Large Cap stocks like Reliance Industries trade over ₹2,000-5,000 crore daily with bid-ask spreads of just ₹0.05-₹0.10. A small-cap stock might trade only ₹5-10 crore daily with spreads of ₹1-5.
Liquidity matters for several reasons. First, it determines the ability to exit a position. A 10,000-share holding in a stock that trades only 5,000 shares per day takes days to unwind and the price moves against the seller in the process. Second, liquidity affects transaction costs - wider bid-ask spreads mean higher round-trip costs to enter and exit positions.
SEBI uses liquidity as a key criterion for Index inclusion and derivative eligibility. To be included in the Nifty 50, a stock must meet stringent liquidity requirements. Similarly, stocks must maintain minimum traded volumes and impact cost thresholds to remain eligible for futures and options trading.
A common position-sizing heuristic among Indian investors is to keep individual position size small relative to daily trading volume - often capped at 1-2 days of average trading volume - so positions can be exited within a reasonable timeframe without significant market impact.
India Context
NSE is among the world's most liquid exchanges by volume. SEBI uses impact cost to measure liquidity for index inclusion. F&O eligibility requires minimum liquidity thresholds.