Volume is the number of shares, contracts or units traded in a period. Traders use it to judge how many participants are behind a price move. A move made on heavy trading is often read as more convincing than the same move made on light trading, because more buyers or sellers had to agree on the new price. This idea is called confirmation, and a move that lacks volume support is often called a weak move.
This guide explains how confirmation and divergence are read, shows how to compare a day's volume with its normal level, and sets out the limits of volume data. Volume is useful context, but it is only as reliable as the data behind it. Some markets report it poorly, and some figures cannot be compared across venues.
What does confirmation mean?
Confirmation means that volume supports the direction of the price. A rising price on rising volume suggests more buyers have joined the move, and a falling price on rising volume suggests more sellers are pushing it down. A move with weak volume is often read as a warning, although only as a tendency rather than a rule.
Divergence in volume is the mismatch between price and trading activity. A new price high on lower volume than the previous high can suggest the rally is attracting less interest. A new high on much higher volume can suggest the reverse. As with other indicators, divergence is easier to spot in hindsight than in real time, and it does not tell you when a move will stop. It is a reason to look more closely at the levels and the trend.
A fall on heavy volume is often read as a sign that sellers are committed, while a fall on thin volume may simply reflect a lack of buyers. Reading the two directions with the same care keeps a trader from treating volume as a signal only when it agrees with a view already held.
How do you compare volume with a normal level?
Raw volume numbers mean little on their own, because a large company trades far more shares than a small one. A better approach is to compare each day with a recent average, such as the average of the past 20 sessions. The ratio is sometimes called relative volume.
A ratio well above 1 suggests unusually heavy trading, and a ratio well below 1 suggests unusually quiet trading.
The table below uses invented figures for a stock whose 20-session average volume is 1.0 million shares. The figures are illustrative.
| Session | Close | Volume (shares) | Relative volume | What it suggests |
|---|---|---|---|---|
| Breakout day | 52.0 | 2.4 million | 2.4 times average | Heavy trading supports the move |
| Next day | 52.6 | 1.5 million | 1.5 times average | Follow-through with decent interest |
| Third day | 52.1 | 0.6 million | 0.6 times average | Quiet trading, the move is losing support |
The breakout day has strong confirmation. The second day adds to it, and the third day shows a fall in interest while the price stalls. The example does not prove what happens next. It shows the kind of evidence a trader would weigh when deciding whether to hold a position, cut it or wait for more data.
The baseline itself needs care. A window that includes a major news event will be inflated, which makes ordinary days look quiet. Some traders use a median instead of a mean, or exclude known event days, so that the baseline reflects normal trading. Whichever method you use, keep it the same across the charts you compare, and write it down so that a later review can follow the same rule.
Why does volume data differ between markets?
Volume figures depend on how a market is organised and how trades are reported. On a single regulated exchange, the reported volume is usually a complete count of the trades on that venue. In a market with many venues, such as many cryptocurrencies, each exchange may report volume separately, and some of the reported activity may not be real.
Some venues report volume in units of the base asset and others in the quote currency, so the same market can show very different figures.
Thin markets are another problem. A stock or coin that trades only a few times a day can show a large jump in volume from a single trade, which makes relative volume misleading. Over-the-counter trades, which are not always reported to the exchange, can also distort the picture. Before you rely on a volume reading, check what the figure measures, which venues it covers and whether the market trades enough for the comparison to mean anything.
How do you read volume on a breakout?
A breakout is more convincing when volume rises as the price moves through the level, and less convincing when the move happens on quiet trading. The most useful comparison is the breakout session against the average of the sessions before it.
A breakout that holds on falling volume afterwards is often read as a sign that buyers are no longer pushing.
Relative volume helps here as well. A breakout session with volume at twice the average shows that many participants took part. The follow-through session matters just as much, because a breakout that continues on fading volume has less support than one that continues on rising volume. Traders often wait for at least one session of confirmation before they treat the move as established.
Volume also helps with false breakouts. A price that goes above a level on light volume and returns inside the range on the next session has not attracted much conviction, while a close back inside the range on heavy volume is a stronger warning. These readings are tendencies. A strong breakout can come on a quiet day, especially in a stock that rarely trades, so volume should be read alongside the other evidence on the chart.
Common mistakes
Reading volume without the price. Volume explains a move only when you know the direction of the price and where it happened.
Using raw volume across different stocks. A large company's volume and a small company's volume are not comparable. Compare each one with its own average.
Trusting a single session. One heavy day can be a news event rather than a shift in interest. Look at several sessions before you draw a conclusion.
Comparing sessions of different lengths. A shortened trading day, such as a session before a holiday, shows lower volume than a normal day even when interest is unchanged. Adjust for the calendar before reading a quiet day as a signal.
Checklist
- Confirm what the volume figure measures and which venues it covers.
- Compare each session with a recent average for the same instrument.
- Check whether heavy volume accompanies the move in the direction of the trade.
- Look for divergence at the price highs or lows you have marked.
- Consider whether a news event explains an unusual day.
- Follow the volume over the next sessions, not only the first one.
- Combine the volume reading with the level, the trend and your stop.
Key takeaways
Volume shows how much trading stood behind a price move. Confirmation means volume supports the direction of the price, and divergence means volume is weakening while the price moves. Comparing each session with a recent average makes the reading meaningful across different instruments. Volume data differs by market, so check what the number measures before you use it.
This guide is for general information, not financial advice. See the disclaimer.