Volume

Volume is the total number of shares traded in a stock during a specific time period (a day, hour, or minute). It measures liquidity and investor interest in the stock.

Formula

Volume = Total Number of Shares Traded in a Period

There's no formula; volume is simply counted. A stock might have 50 million shares traded on Monday but only 10 million on Tuesday.

Example

Apple (AAPL) typically trades 50-60 million shares per day. On a day when AAPL reports earnings, volume might spike to 150 million shares because many more investors are buying and selling. High volume on an earnings day indicates strong interest in the news.

How to Interpret It

• High volume on up days: Bullish signal. Strong buying interest is driving the price up.
• High volume on down days: Bearish signal. Strong selling pressure is driving the price down.
• Low volume on up days: Weak bullish signal. The rally lacks conviction.
• Low volume on down days: Weak bearish signal. The selloff lacks conviction.
• Volume spikes: Sudden volume increases often occur on news (earnings, FDA approval, CEO change). Higher volume confirms the move's significance.
• Volume trend: Rising volume over time suggests growing investor interest; declining volume suggests waning interest.
• On-balance volume: Cumulative volume combining direction (up or down days) to show whether volume is accumulating or distributing.

Limitations

• Volume alone doesn't indicate direction. High volume can accompany up moves or down moves.
• Volume data from different venues (exchanges, OTC, dark pools) may not all be captured in the reported figure.
• Past volume doesn't predict future volume.
• Very high volume spikes can be due to news or technical reasons and don't always continue.

Related Terms

• Average Volume — typical daily volume over a longer period
• Liquidity — ease of buying and selling without affecting price
• VWAP — average price weighted by volume
• Bid-Ask Spread — the gap between buyers and sellers, related to liquidity