Volume & money flowOn-Balance Volume · OBV
A running tally that adds the day's volume on up-closes and subtracts it on down-closes — Granville's classic accumulation gauge.
Works best in trending marketsEngine-computed on a fixed sample series
What it is
On-Balance Volume, or OBV, is a cumulative volume indicator created by Joe Granville that keeps a running tally of volume, adding it on days price closes up and subtracting it on days price closes down. The premise behind it is Granville's famous claim that volume precedes price — that changes in buying and selling pressure show up in volume before they become visible in price itself — so a rising OBV line reveals accumulation building beneath the surface even before a breakout. For a beginner, OBV is a way to gauge whether the crowd is quietly buying into or selling out of an instrument by watching whether volume is flowing in on up-days or out on down-days. It is one of the oldest and most widely used volume indicators, valued especially for confirming trends and for spotting divergences where volume and price disagree. The single OBV line distills the entire history of up-versus-down volume into a running measure of net buying pressure.
How it is calculated
OBV is a simple cumulative sum with a directional rule. Each day you compare the close to the previous close: if today's close is higher, you add the full day's volume to the running OBV total; if today's close is lower, you subtract the full day's volume; and if the close is unchanged, OBV holds steady and volume is neither added nor subtracted. The calculation uses the entire session's volume based solely on the direction of the close, without regard to how large the price move was — a one-cent up-close adds exactly as much volume as a large up-close. The starting value is arbitrary, so OBV begins from a chosen baseline and accumulates from there, which means the absolute number it reaches carries no independent meaning. What matters is the resulting line's direction and shape over time, which reflect the net flow of volume into or out of the instrument.
Reading it, step by step
The absolute value of OBV is meaningless because it depends entirely on where the count started, so you read only its slope and its divergence from price. A rising OBV line means volume is accumulating on up-days and confirms an uptrend, showing that buying pressure supports the advance; a falling OBV confirms a downtrend. The most powerful read is divergence: when price makes a new high but OBV fails to make a corresponding new high, it signals that the rally is not backed by volume and distribution may be underway beneath the surface, a bearish warning; the mirror at lows, where price makes a new low but OBV holds up, hints at accumulation and a possible bottom. Some traders also draw trendlines directly on the OBV line and treat a break of an OBV trendline as an early signal, since under Granville's thesis the volume move may lead the price move. The core is always slope and divergence, never the raw level.
Best timeframes and settings
OBV has no adjustable parameters — it is a pure cumulative sum — so the only choice is the chart timeframe on which you apply it. It works across horizons, from intraday charts for active traders to daily charts for swing trading and weekly charts for long-term trend confirmation, with daily being the most common. Because it has no smoothing, some traders overlay a moving average of the OBV line to smooth its wiggles and generate crossover signals, effectively adding a parameter the base indicator lacks. The trade-off there is the usual one: a shorter moving average of OBV reacts faster but whipsaws more, a longer one is steadier but slower. OBV depends on reliable volume data, so it is best applied to centralized, high-volume instruments where the volume series is clean and consistent, and it is weaker on assets with fragmented or synthetic volume.
When and where to use it
OBV is best used as a confirmation overlay in trending markets, where its slope validates that volume supports the price trend and its divergences warn when that support is failing. It excels at confirming breakouts — a breakout accompanied by an OBV breakout is more trustworthy than one where OBV lags — and at flagging early warnings through divergence at tops and bottoms. It works well on liquid stocks, index ETFs, and futures with dependable volume. It is a supporting tool rather than a standalone system, so it should confirm signals from price and other indicators rather than generate trades alone. Avoid over-relying on it in choppy, directionless markets where its line drifts without meaning, and be cautious on instruments where volume is unreliable, since the entire calculation rests on the integrity of the volume data. Its strength is confirmation and divergence, not precise timing.
Strategies that use it
The confirmation strategy uses OBV to validate breakouts: you take a price breakout above resistance more seriously when OBV simultaneously breaks above its own recent range, confirming that volume is flowing in to support the move, and you distrust a breakout that OBV does not confirm. The divergence strategy treats a disagreement between OBV and price as an early warning — when price makes a new high while OBV makes a lower high, you tighten stops or stand aside ahead of a likely reversal, and the bullish version at lows cues you to look for a bottom. A third, trend-following strategy applies technical analysis to the OBV line itself, drawing trendlines on OBV and acting when they break, or trading crossovers of OBV through a moving average of itself, on the logic that OBV's move may precede price. Each strategy uses OBV to confirm or anticipate rather than as an isolated trigger.
Combining it with other indicators
OBV pairs naturally with price-based tools like support and resistance and trendlines, where it confirms whether a level break has volume behind it. It complements other volume indicators — the Price-Volume Trend, the Accumulation-Distribution Line, and Net Volume — each of which weighs volume slightly differently, so agreement among them strengthens the accumulation-or-distribution read while disagreement flags ambiguity. Momentum oscillators such as RSI and MACD combine well with OBV divergences, since a bearish OBV divergence that coincides with a bearish RSI divergence is far more compelling than either alone. Moving averages of price give trend context that OBV then confirms or questions. Because OBV is a confirmation tool, it is most effective layered beneath a primary price or momentum method, adding a volume dimension to signals those tools generate rather than standing as the sole basis for a trade.
Where it fails
OBV's crudest flaw is that it counts the entire day's volume based on a single up-or-down close, so a marginal close flips the whole bar's contribution — a tiny up-close and a huge up-close add identical volume, making the indicator blunt about the actual size of a move. A single high-volume session, such as a gap on news or an index rebalance, can add or subtract a huge slug of volume and distort the OBV line for weeks afterward. It gives no weight to where within the range price closed, unlike the Accumulation-Distribution Line, so it can miss the nuance of a bar that reversed intraday. Divergences can persist far longer than expected before price responds, so an OBV divergence is a warning rather than a precise timing signal. And because it depends wholly on volume data, it misleads on instruments where that data is fragmented, synthetic, or unreliable, which is why OBV is a supporting tool and never a standalone system.
A worked example
Imagine a stock consolidating just beneath resistance at 50, with its OBV line, started from an arbitrary baseline, grinding steadily higher over the same weeks — even though price is flat, volume is accumulating on the up-days, hinting under Granville's thesis that buyers are quietly positioning before a move. When the stock finally breaks above 50, OBV simultaneously pushes to a new high of its own, confirming the breakout is backed by real volume, and you enter long with added confidence. The stock advances to 58 over the following weeks, but you then notice that as price edges to a marginal new high near 60, OBV makes a distinctly lower high — a bearish divergence signaling the rally is no longer supported by accumulating volume and distribution may be setting in. You take this as a cue to tighten your trailing stop, which exits you near 57 as price rolls over, and the OBV divergence proves prescient when the stock subsequently falls back toward 50, having warned that the buying pressure beneath the final push higher had quietly dried up.