What volume is
Volume is the number of shares that change hands in a period: a day, an hour or a minute. Every trade has a buyer and a seller, so a trade of 100 shares adds 100 to volume, not 200. Volume says how much trading happened, not which way it pushed the price.
Dollar volume = shares traded × price. It compares activity across stocks with very different share prices: 1 million shares of a $10 stock is $10 million of trading; 1 million shares of a $500 stock is $500 million.
How volume is shown
- Volume bars: a column under each price bar or candle, one per period. The taller the column, the more shares traded. Most charts colour a bar green when the price closed higher than the period before and red when it closed lower; some compare the close with the open instead.
- Average volume line: a simple moving average of volume, usually 20 or 50 days, drawn across the bars. Bars well above it stand out.
- Relative volume (RVOL): today's volume / average volume. An RVOL of 2 means twice the usual trading. Intraday versions compare with the average volume up to the same time of day, because trading bunches up at the open and the close.
- Volume profile: a sideways histogram along the price axis showing how many shares traded at each price over a window. Prices where a lot changed hands often act as reference points later.
Why volume matters in an efficient market
The efficient market idea says prices quickly reflect public information. Trading is how that happens: when news arrives, investors who read it differently trade with each other until the price settles where buyers and sellers balance. Volume is the record of that process.
- Information arrives as volume. Volume jumps on earnings, guidance and economic releases. The heavier the volume, the more investors took part in setting the new price.
- Conviction. A move on heavy volume reflects many participants agreeing to a new price. A move on thin volume was set by fewer of them and can reverse more easily.
- Liquidity and cost. Heavily traded stocks have narrow bid-ask spreads and absorb large orders with little price impact, so their prices adjust to news fastest. Thinly traded stocks cost more to trade, and mispricings last longest there, which also makes them hardest to profit from.
- Attention. Studies have found that stocks with unusually high volume over a day or a week tend to do slightly better over the following month, the "high-volume return premium" (Gervais, Kaniel and Mingelgrin, 2001). The likely reason is that the trading brings the stock to more investors' attention.
Volume does not make a market less efficient; it is how a market becomes efficient. Reading volume is reading how many people took part in the latest price, and how strongly they agreed with it.
Reading volume with price
| Price | Volume | Usual reading |
|---|---|---|
| Rising | Rising | Strong buying: the move has support |
| Rising | Falling | Weak rally: fewer buyers each day |
| Falling | Rising | Strong selling, often called distribution |
| Falling | Falling | Selling is drying up |
- Breakouts: a move above a past high on one and a half to two times average volume is more trustworthy than one on light volume.
- Capitulation: after a long fall, a day of extreme volume and a sharp drop can mark the point where the last sellers give up. It is only clear afterwards.
- Divergence: the price makes a new high while volume on rising days keeps shrinking. As with MACD divergence, the move may be running out of buyers.
Volume indicators
| Indicator | Formula | Shows |
|---|---|---|
| Average volume | Average of the last N days' volume | The normal level to compare against |
| Relative volume | Today's volume / average volume | How unusual today is |
| On-balance volume (OBV) | Yesterday's OBV, plus today's volume if the close rose or minus it if the close fell | Whether volume flows in on rising days or falling days |
| VWAP | Sum of (typical price × volume) / sum of volume, since the open | The average price paid today, weighted by size |
On-balance volume was introduced by Joseph Granville in 1963. Its level means nothing; its direction does. A rising OBV while the price moves sideways suggests buyers are quietly building positions.
VWAP (volume-weighted average price) restarts every day. Each bar's typical price is (high + low + close) / 3. Large funds use VWAP to judge their own trades: buying below it counts as a good fill. When the price is above VWAP, the average buyer today is in profit.
Limits
- Volume has no direction. Every share bought was also sold. Green and red bars show only which way the price closed.
- Trading is split across many venues. US stocks trade on more than a dozen exchanges and off exchange, in dark pools and with wholesale market makers, which together have handled a large share of all volume in recent years. A feed from one exchange shows only that exchange's slice: IEX, for example, handles a few percent of all trading. Compare a stock's volume only with the same feed's own history.
- Some days are distorted. Index rebalances, quarterly options expirations and the last day of a quarter bring heavy volume that says little about investors' views.
- ETFs trade more easily than their volume suggests. Market makers can create and redeem ETF shares against the fund's holdings, so a quiet ETF that holds busy stocks can still be cheap to trade. Check the bid-ask spread as well as the volume.
- It says nothing about the business. On this site, volume is a check on a price move, not a reason to own a company. See Fundamentals vs technicals.
Options volume
Options have volume too, counted in contracts rather than shares, along with open interest: the number of contracts still open. Both are covered in Options analysis.
Questions
What is high volume for a stock?
There is no fixed number. Compare a day's volume with the stock's own average: one and a half to two times the 50-day average is heavy, and under half is light.
Does high volume mean the price will rise?
No. Volume shows how much trading happened, not which way. Heavy volume on a falling day is heavy selling.
See also
- Options analysis Options as a technical indicator: the Greeks and their formulas, open interest, the put/call ratio, implied volatility, and reading options heatmaps.
- Momentum investing What price momentum is, the evidence that recent winners tend to keep winning for a while, how momentum is measured, and its crash risk.
- MACD indicator How the MACD indicator is built from two exponential moving averages, what the signal line and histogram show, and how crossovers are read.
- Fundamentals vs technicals The difference between fundamental and technical analysis, what each is good for, and why this site uses fundamentals to choose and technicals only as context.
Last updated October 16, 2026. Education only, not investment advice.