On-Balance Volume (OBV): Using Volume to Confirm Price Trends
OBV accumulates volume in the direction of price to measure money flow. We explain how it is calculated, how to use it to confirm trends, and how to spot divergence between price and volume.
Does volume "lead" price?
There is a saying in technical analysis: "volume precedes price." OBV (On-Balance Volume) turns that idea into an indicator: accumulating volume in the direction of price to measure cumulative buying/selling pressure — showing whether money is quietly flowing in or out.
How OBV is calculated
The principle is very simple:
- On a day the price closes up: add that day full volume to OBV.
- On a day the price closes down: subtract that day full volume from OBV.
- Price flat: OBV unchanged.
The result is a cumulative line. The absolute value of OBV does not matter — what matters is the direction and slope of the OBV line.
How to use OBV
1. Confirm the trend:
- Price up + OBV up means the uptrend is "supported" by volume, reliable.
- Price up but OBV flat/down means the rise lacks volume, suspicious.
2. Spot divergence between price and volume:
- Price makes a higher high but OBV makes a lower high means money is leaving even as price rises, warning of a downward reversal.
- Price makes a lower low but OBV makes a higher low means money is flowing in even as price falls, warning of an upward reversal.
This is the most valuable application of OBV — spotting "quiet accumulation" (big money buying) or "distribution" (selling) before it shows up clearly in price.
Why OBV is useful
OBV reflects money flow, which is harder to "fake" than price. A price rally not backed by rising OBV is usually a weak signal. The idea that "volume confirms the trend" is also one of the tenets of Dow Theory.
Limits
- A relative indicator: OBV shows the direction of money flow, not a specific price level.
- Sensitive to volume spikes: one abnormal-volume session can skew OBV.
- Needs to combine: use OBV with price, trend, and other indicators — not alone. Always pair it with risk management.
Conclusion
OBV accumulates volume in the direction of price (adding on up days, subtracting on down days) to measure cumulative money flow. Use it to confirm trends (price and OBV agreeing is reliable) and to spot price-volume divergence warning of reversals. What matters is the direction of OBV, not its absolute value — and always combine with other signals.
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