Price tells you where a market has been. Volume tells you how much conviction was behind the move. On-balance volume, usually shortened to OBV, is one of the simplest ways to combine the two. It was popularised by the market analyst Joe Granville in the 1960s, and it is still found on almost every charting platform. Here is how it works and how traders use it.
How OBV is calculated
OBV is a running total. Each day, if the price closes higher than the day before, that day’s trading volume is added to the total. If it closes lower, the volume is subtracted. If the close is unchanged, the total stays the same.
The actual number on the chart is not meaningful in itself, because it depends on where the calculation started. What matters is the direction and shape of the line. A rising OBV line suggests that more volume is flowing in on up days than down days, which is often read as accumulation, or buying pressure. A falling line suggests distribution, or selling pressure.
The idea behind it
Granville’s view was that volume often moves before price. If large investors are quietly building a position, volume on up days should start to outweigh volume on down days, even before the price breaks out. OBV is designed to make that shift visible.
How traders use it
Confirming a trend. In a healthy uptrend, both price and OBV should be making higher highs. If price rises and OBV rises with it, the move has volume behind it. Our guide to market structure explains how highs and lows define a trend.
Spotting divergence. When price and OBV disagree, traders take note. If a share makes a new high but OBV fails to, the rally may be running on thin participation and could be vulnerable. If price makes a new low but OBV holds up, selling pressure may be fading. Divergence is a warning sign, not a signal to act on alone.
Checking breakouts. When price breaks above a resistance level, a matching jump in OBV suggests real buying. A breakout without an OBV move is more likely to fail, which links to our explainer on bull traps.
Where OBV misleads
OBV treats every day as all-or-nothing. A share that closes up by a penny on huge volume gets the full volume added, even though the day was effectively flat. That can distort the line, especially around big news days.
One unusual day, such as an index rebalancing, a block trade or results, can create a big spike that dominates the line for weeks afterwards. It is worth checking whether a sudden OBV move was caused by a one-off event.
OBV also depends on reliable volume data. In stocks and futures, volume is reported centrally. In the spot currency market there is no single central exchange, so the volume shown on many charts is only a partial measure, often tick volume from one broker. OBV is therefore much less reliable for forex than for shares.
Using it sensibly
Like most indicators, OBV works best as supporting evidence rather than a trading system on its own. Many traders look at it alongside price structure and one or two other tools, rather than piling indicators onto a chart. Our piece on the mistake of cluttering your chart explains why less is often more.
The bottom line
On-balance volume is a simple way to see whether volume is backing a price move. Rising price with rising OBV suggests conviction; divergence suggests caution. It has real blind spots, especially in forex and around one-off events, so treat it as a second opinion rather than the final word. If you want to know how well your analysis process holds together, take the free Samuel & Co Trading Trader Assessment.
