Volume and what it tells you
Price tells you what happened. Volume tells you how much conviction was behind it. It's the one input in technical analysis that comes from actual participation rather than from price itself.
The core principles
- Confirmation: a breakout on heavy volume is more credible than one on light volume, because more participants are committing.
- Divergence: a rally on shrinking volume suggests fewer buyers are willing to pay higher prices.
- Climax: extreme volume after a long move often marks exhaustion, a capitulation low or a blow-off top.
- Context: volume is relative. Compare today with the stock's own average (relative volume), not with other stocks.
Where volume comes from
Volume isn't spread evenly. It clusters at the open and close (closing auctions are where many index funds trade), around news, earnings and economic data, and on options expiry and index rebalancing days. A volume spike on a rebalance day says little about conviction. Knowing why volume arrived matters as much as how much.
Common volume tools
- Volume bars: the simplest view, usually under the price chart.
- On-balance volume (OBV): adds volume on up days and subtracts on down days to track accumulation or distribution.
- VWAP: the volume-weighted average price, the institutional benchmark (lesson 5.2).
- Volume profile: volume by price level instead of by time. High-volume nodes show where the market accepted price, and often act as support or resistance. Low-volume gaps tend to be crossed quickly.
Limits
Much volume now trades off-exchange and in dark pools, and some reported volume is market makers trading with each other. In crypto, volume on some exchanges has historically been inflated. Use volume from reliable, consolidated sources, and treat it as evidence, not proof.
Key takeaway
Volume shows commitment. Moves backed by volume deserve more respect, and moves that fade on volume deserve more scepticism.
Educational content only, not financial advice. Investing involves risk and you can lose money.