Volume
Number of shares traded in a period.
Volume is the total number of shares traded in a given time interval — typically a full trading day, but calculable by the hour, minute, or week as well. It is one of the few technical indicators that measures not price but the flow of activity around a stock.
High volume is associated with more 'credible' price moves: a 5% rally on volume three times the average suggests market conviction; the same 5% on thin volume suggests a fragile move that can reverse easily. The same logic applies to declines.
Worked example
Apple has a 50-day average daily volume of roughly 50 million shares. On earnings days volume typically rises to 150–200 million — three to four times the average. On quiet sessions with no news it can fall to 35–40 million. A single session with 100 million shares traded signals that something attracted attention: a news item, an analyst upgrade or downgrade, a macro sector event, or the entry or exit of a large institutional holder.
By contrast, a small-cap stock on a secondary exchange may average 10,000–50,000 shares per day. A single institutional investor seeking to buy 200,000 shares could move the price 5–10% purely through pressure on supply. Managing exposure in low-volume stocks requires limit orders and patience.
When it's used
Volume serves three primary purposes. First, validating a price move: a breakout above resistance on volume 2x the average is more reliable than one on normal volume. Second, identifying institutional interest: large funds move volumes that stand out from the retail crowd, and their entry or exit tends to precede sustained price moves. Third, screening: 'stocks with today's volume greater than 3x the average' is a classic filter for identifying unusual activity — usually linked to news.
Limits
Exchange-reported volumes do not include dark pools, institutional trading platforms where 30–40% of U.S. equity volume trades away from lit exchanges. Public volume data is therefore a subset, not the total. Volume must also always be compared against the stock's own historical average, not against absolute values: 10 million shares is high for a small cap but low for Apple.
Frequently asked
Is low volume always a bad sign?
Not necessarily. Many defensive names (consumer staples, utilities) have structurally lower volume than tech stocks. The right question is 'is today's volume consistent with this stock's average?', not 'is it high in absolute terms?'
What does 3x average volume mean?
It means three times as many shares changed hands today as on an average day over the past 50 sessions. It signals that something notable occurred: a news release, an analyst rating change, a macro sector event, or the entry or exit of a large institutional holder.
Are dark pool trades included in public volume?
No. Dark pool trades are OTC transactions that do not flow through lit exchanges. They are typically reported with a delay (T+1 or later) and in aggregate. The 'volume' figure you see on a broker platform is exchange volume only, not total market volume.
Related terms
Educational definition. Not financial advice.