What it means
The indicator was developed by Joseph Granville and popularised in his 1963 book on market timing. The idea is that volume comes before price: if heavy buying is happening, volume will build up before the price visibly breaks higher.
On-balance volume turns that idea into a single line that can be drawn under a price chart. The calculation is simple.
If today's closing price is higher than yesterday's, the whole day's volume is added to the total. If it is lower, the volume is subtracted, and if it is unchanged the total stays the same.
The absolute number means little because it depends on where the series began. What traders watch is the direction and the pattern.
A rising line during a rising price supports the trend, while a flat or falling line during a rising price is a warning that the move may lack support. Divergence is the most common signal.
If the price makes a new high but on-balance volume fails to do so, the move may be weak. If the price is falling but the volume line is rising, accumulation by buyers may be under way.
There are limits. The method assigns a day's full volume to the buyers or sellers whether the price moved by a cent or by several dollars, so it ignores the size of the move.
It also gives no signal about timing, so most users combine it with other tools such as trend lines or moving averages.
In practice
Real-world examples.
Example
A trader notices a stock edging up to a new high of $42 but with on-balance volume lower than at its previous peak. She treats the breakout as suspect and takes profit on part of her $20,000 position rather than adding to it.
Example
An analyst at a small investment firm sees a share price drifting sideways for two months while on-balance volume climbs steadily. He concludes that buyers are quietly accumulating and recommends a starter position of $50,000.
Example
A portfolio manager checks the on-balance volume of an index fund after a sharp one-day rally. Volume that day was below average, and the indicator barely moves. She decides to wait for confirmation before putting new money to work.
Formula
Calculation
OBV today = OBV yesterday + volume today (if close today is above close yesterday)
OBV today = OBV yesterday - volume today (if close today is below close yesterday)
OBV today = OBV yesterday (if the close is unchanged)
Suppose a stock starts with an OBV of 0 and trades as follows.
Day 1: close $50.00, up from $49.00, volume 20,000, so OBV = 0 + 20,000 = 20,000.
Day 2: close $50.50, up, volume 30,000, so OBV = 20,000 + 30,000 = 50,000.
Day 3: close $50.20, down, volume 10,000, so OBV = 50,000 - 10,000 = 40,000.
Day 4: close $50.20, unchanged, volume 15,000, so OBV stays at 40,000.
Day 5: close $51.00, up, volume 25,000, so OBV = 40,000 + 25,000 = 65,000.
The line rose from 0 to 65,000 while the price rose from $49.00 to $51.00, so volume supported the move.Case study
Seen in the real world.
Kestrel Securities is an illustrative, fictional brokerage whose research desk tested on-balance volume on a basket of 40 mid-sized shares. The desk wanted to know whether divergences between the price and the indicator gave useful warnings.
Over a year, the analysts flagged 25 cases where the price rose to a new high while on-balance volume did not. In 15 of those, the price fell back by at least 5% within a month, and in the remaining 10 it kept rising.
The head of research concluded that the signal was helpful but far from reliable, and advised clients to use it as one input alongside valuation and trend. The illustrative lesson is that technical indicators suggest probabilities, not certainties.
Watch out
Common mistakes.
- Reading the absolute value of on-balance volume as meaningful, when only its direction and its relationship to price matter.
- Treating a divergence as an instant sell or buy signal, when it only suggests the trend may be weakening.
- Ignoring the size of the price change, since the indicator counts a tiny move the same as a large one.
Questions
People also ask.
Who created on-balance volume?
Joseph Granville developed it and described it in his 1963 book, and it remains one of the best-known volume indicators.
What does a rising on-balance volume line mean?
It suggests that more volume is trading on up days than on down days, which is usually read as buying pressure.
Can it be used for any security?
It can be applied to any market with reliable volume data, such as shares and exchange-traded funds, but it is less useful where volume is thin or poorly reported.
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