Trading Volume
The number of shares bought and sold over a given period — a measure of how much actual trading took part in a price move.
Volume = number of shares traded in the period (e.g., one day)
When the price rises and volume rises with it, the advance is seen as having strength behind it.
In plain terms
Even for the same 1% gain, a rise driven by just a few trades carries different weight than one where a great many people piled in. Volume shows "how much actual trading took part in that price change."
One point worth noting: volume itself has no direction. Whatever someone bought, someone else sold. So what volume tells you is not "whether the price will rise or fall," but "how much interest and conviction was behind that move."
What it tells you
Volume is an easier signal to trust than price. A share price can be pushed up or down briefly with only a small amount of stock, while volume simply shows how much trading actually took place. So a price that keeps rising on thin volume may be a weak move created by only a handful of trades.
When volume suddenly jumps well above its usual level, it signals that something drew attention — an earnings release or major news. That said, a rise in volume alone does not mean the attention was favorable. Volume figures alone cannot tell you who bought and who sold those shares.
Formula
Volume = number of shares traded in the period (e.g., one day) Turnover = volume × trade price (Since every trade has a buyer and a seller in equal amounts, volume itself does not indicate whether prices went up or down.)
What high or low means
When the price rises and volume rises with it, the advance is seen as having strength behind it. Conversely, when the price rises while volume shrinks (especially at new highs), it means fewer people are joining in, and it is sometimes read as a sign that the advance is losing steam. When price and volume point in different directions like this, it is called "volume divergence."
⚠ Sometimes it works the opposite of intuition. When volume suddenly surges while the price is near a peak, it may look like a good sign, but it can actually be a process in which shares change hands — latecomers buying up the stock that large investors are releasing. "Lots of trading" does not mean "lots of buyers."
High volume is not good and low volume is not bad. It is a supplementary indicator for seeing "how much conviction was behind a price change," not which direction the price will go.
On earnings dates, options expiration days, and index inclusion dates, volume spikes temporarily. So a single day's figure takes on meaning only when compared with the usual average.
For small-cap stocks with thin volume, even a few trades can swing the price sharply, and it is hard to buy or sell at the price you want (this is described as "lacking liquidity"). Volume is also an indicator unrelated to a company's value, and in itself is not a signal to buy or sell.
During the 2021 GameStop (GME) episode, volume exploded and the share price rose sharply over a short period. But much of that volume came from crowd psychology and a short squeeze rather than from the company's results, and once the heat faded the price fell quickly.
It is a case showing that the simple idea that "a big rise in volume means good interest has gathered" is not always right. Volume tells you how hot the market is, but not why it is hot.
Metrics to read alongside
Guides that cover this term
See it in real stocks
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This explanation is for information and reference only and is not a recommendation to buy or sell any security. Investment decisions and their consequences are your own.