What OBV measures: volume with a direction, accumulated
OBV (On Balance Volume) is a cumulative line built by attaching a plus or minus sign to each bar's volume and adding it up continuously. Joseph Granville popularized it in a book in the 1960s, and today it is a default indicator in most charting programs. Ordinary volume bars show only how much each bar traded and are not connected, but OBV joins those bars into one line according to the direction of the close. Over time, whether more volume sat on rising bars or on falling bars shows up as the slope of the line. The idea Granville attached to it was that volume moves before price: when large participants accumulate quietly, more trading lands on rising bars even while price is still flat, and the trace appears in OBV first. That explanation is one interpretation, not a proven law, and this guide treats it that way. Basic volume concepts, such as the difference between volume and turnover or spike multiples, are covered in the Volume Analysis guide; here we look closely at the single line that is OBV.
Definition and calculation
The rule of OBV is simple. If this bar's close is higher than the previous close, add this bar's volume to the previous OBV; if lower, subtract it; if equal, keep the previous OBV. For example, starting from an OBV of 1,000, a bar whose close rose on volume of 300 brings it to 1,300, and if the next bar's close falls on volume of 200, it becomes 1,100. It does not use how far price moved within the bar or where the high and low were; only the direction of the close and the volume. It also differs from other indicators in having no period setting. TradingView's default OBV starts accumulating from the first bar the chart receives, and the first bar starts at 0 because there is no previous close to compare. When the line is too jagged, some people overlay a moving average on OBV to see its direction; a length of around 20 bars is common, but there is no fixed standard. This moving average only smooths OBV and adds no new information to the calculation.
- Close > previous close: OBV = previous OBV + this bar's volume
- Close < previous close: OBV = previous OBV − this bar's volume
- Close = previous close: OBV = previous OBV
- The first bar has no previous close, so it starts at 0
A different start gives the same shape: slope over value
The OBV number itself carries almost no meaning. Depending on where accumulation began, the value at the same point can be in the millions or negative. If one tool calculates from only the last 500 bars and another from several years of data, the OBV numbers for the same stock on the same day will be completely different. Yet the shape of the two lines, meaning where they rose and where they fell, is the same, because a different starting point only shifts the whole line up or down in parallel. So with OBV you look at 'which way it has been tilting recently' rather than 'what it is now'. For the same reason, comparing OBV numbers across different assets is meaningless. If you want to compare, the fairer approaches are to compare the current position against recent highs and lows within each asset, or to divide how much OBV changed over a period by the total volume of that period to turn it into a ratio. Whether the number is above or below 0 is also set by the starting point, so it cannot serve as a reference line.
How to read it: does it move with price?
The most basic reading is whether OBV and price move the same way. If OBV makes higher highs as price makes higher highs, it is read as volume steadily landing more on rising bars. If OBV makes lower lows as price makes lower lows, more volume is landing on falling bars. When the two move together like this, people often say OBV confirms the trend. In a range OBV also tends to move sideways, and some watch whether its slope gradually tilts to one side inside the range. When reading, match highs and lows in price and in OBV at the same points in time. Comparing two lines by eye makes it easy to see what you want to see, so it is better to first choose the high or low to compare on the price chart and then find OBV on that bar. And OBV moving with price is a summary that trading accompanied the move so far, not a guarantee that the move will continue (see the Trend guide).
How to read it: divergences and OBV crossing first
The most discussed scene in OBV is when price and OBV diverge. If price makes a new high but OBV fails to exceed its previous high, it is read as volume not following the rise, a clue that the move is weakening. Conversely, if price makes a new low while OBV stays above its previous low, it is read as less volume landing on falling bars. Such divergences have the same structure as RSI divergences and share the same weakness: they appear or disappear depending on how highs and lows are chosen (see the Divergence guide). Another reading Granville stressed is OBV breaking above its own high or trendline before price does. If price is still inside a range but OBV first exceeds its high for that range period, the interpretation is that trading is leaning to one side. But it is common for price to carry on unchanged for a long time after a divergence or an early breakout, and OBV often drifts back with nothing happening. These scenes are clues, not conclusions.
The weight of a single bar, and similar cumulative indicators
OBV's rule adds a bar's entire volume even if the close rises by the smallest amount. A bar that fell sharply all day and then closed one tick above the previous close right before the end still adds all its volume as a plus. So one bar with several times normal volume can change OBV's direction for a long time because of a tiny difference in the close. Some indicators try to refine this roughness. The accumulation/distribution line (A/D) adds or subtracts only part of the volume depending on where the close ended between the bar's high and low: nearly all of it when the close is at the high, close to zero when it is in the middle. Chaikin Money Flow (CMF) applies the same idea summed over a fixed window and shows it as a ratio; a common default is 20 bars. In exchange for using the position within the bar, these indicators have their own weaknesses, such as not capturing gaps. Rather than one being better, they are useful for checking, when OBV and these say different things on the same chart, whether a single bar's close dragged OBV along.
Common misconceptions
A few misconceptions come up often with OBV. First, reading a rising OBV as 'more people are buying'. Every trade matches a buyer and a seller in the same quantity, so a rising OBV only means volume was larger on bars where the close rose, not that the quantity bought exceeded the quantity sold. Second, comparing OBV numbers with other tools or other assets. As shown above, the number is set by the starting point. Third, taking divergences as forecasts that always come true. Looking back at a chart, divergences before big turns stand out, but divergences that passed with nothing happening are not remembered. Fourth, not checking where the volume data comes from. Whether it is the volume of one exchange or several exchanges combined can change the shape of OBV. Below are points worth keeping in mind when looking at OBV.
- A rising OBV means 'more volume on rising bars', not 'more buying'
- The number is set by the starting point; do not compare numbers across tools or assets
- The divergences you remember are the ones that worked; many others passed by
- The shape changes with which exchange and trading pair the volume comes from
What looks different in crypto and stocks
A coin's OBV differs by exchange. Even for the same Bitcoin, OBV on Binance's BTCUSDT chart includes only trades in that pair, leaving out other exchanges, Korean won markets and futures. On a day when only the won market was busy on domestic news, OBV on an overseas exchange's chart might barely move. Crypto also trades around the clock, so bars from quiet early-morning hours are each added or subtracted, and the shorter the bar, the more of these thin bars there are. Stocks center on regular-session trading, and large volume around the open and close is a normal pattern. Heavily traded stocks like Samsung Electronics or SK hynix have relatively smooth daily OBV, but on days with earnings reports or index additions and removals, a single large-volume bar can bend the line sharply. After a stock split, OBV can change shape like a step depending on whether past volume was adjusted to the new share count. US indexes themselves have no volume or have it attached differently by each tool, so index OBV is often viewed through the volume of an exchange-traded fund (ETF) that tracks the index instead.
On a live chart
On a live chart the rightmost bar has not closed, and its effect on OBV is the least stable. The volume of the bar in progress keeps accumulating over time, and whether that volume is added or subtracted depends on whether the current price is above or below the previous close. So when the current price hovers around the previous close, all the volume accumulated so far flips between plus and minus each time, and the end of OBV jumps up and down sharply. If a lot of volume has built up near the end of the bar, the swing is even larger. Therefore, judgments such as OBV highs and lows, divergences or trendline breaks should be made after the bar closes. On short bars it is common for the end of OBV to bend the other way within seconds, and reading that as trading leaning to one side is a mistake. Also, if the number of bars a tool receives grows or shrinks, the starting point changes and the number can suddenly differ; this too changes only the number, not the shape, so there is no need for alarm.
A practical checklist
Checking the items below in order before reading OBV avoids many of the common misconceptions. If any one of them applies, take the meaning you read from OBV down a notch. The key to the order is to start from price. First choose the highs and lows to compare on price, then look at OBV on the same bars, and finally recheck on the volume bars whether a single large-volume bar dragged the line. Placing the volume bars and OBV side by side on one screen makes this last check easier. On a day when a scanner that lines up many stocks in one table shows several with trading leaning to one side, that is usually the result of the whole market moving together and does not amount to as many pieces of evidence as there are stocks. Looking at the same scene on a different bar length also helps. If a divergence visible on 1-hour bars does not appear on daily bars, the time span it covers is short. OBV is supplementary information that adds how much trading accompanied what price said; it does not replace price action.
- Which exchange and trading pair, or which ETF, the volume comes from
- The bar length, and from which bar the tool started accumulating (look at the shape, not the number)
- Whether the last bar is closed or still in progress
- Whether you set price highs and lows first and compared OBV on the same bars
- Whether a single bar with several times normal volume changed the direction
- Whether other cumulative indicators such as the A/D line say the same thing
Limits and disclaimer
OBV is built from only two pieces of information: the direction of the close and volume. It cannot tell what happened within the bar, who traded and why, or whether those trades were really between different participants. In a market with inflated volume, OBV is inflated just as much. Granville's idea that 'volume moves before price' is also an interpretation that fits some scenes, not something confirmed as a law that holds regardless of market and period. Scenes on past charts where OBV turned before price look impressive mostly because they were picked after the outcome was known. So this guide does not present OBV's slope or divergences as a rule for when to buy or sell, and does not claim that any particular reading will keep working. This guide is educational material explaining what the indicator means and how to read it, not investment advice. Trading decisions and their results rest with each person.
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