OBV Detailed: Granville's Cumulative Volume Line

Key Takeaways

• OBV adds full bar volume when the close is up and subtracts it when the close is down, with no change on flat closes.
• Granville's central idea is that volume precedes price, so OBV turns can foreshadow price turns.
• The absolute level of OBV is arbitrary; only direction, slope, and divergences carry information.
• Treating every minor OBV wiggle as a signal is the most common error among new users of the line.

What It Is

OBV is one of the earliest momentum-of-volume indicators in the technical analysis literature. It plots a single line that grows when buyers dominate the closes and shrinks when sellers do.

Because the starting value is arbitrary, two platforms can show very different absolute OBV numbers for the same stock. What matters is whether the line is making higher highs and higher lows, lower highs and lower lows, or diverging from price.

The Intuition

Granville argued that volume is the fuel of price moves. If a stock is making new highs but the cumulative volume line is not, the rally is running on fumes. If price is grinding lower but OBV is holding firm, accumulation may be quietly building.

The OBV line strips a lot of complexity out of that idea. You do not need to weight individual trades or guess at order flow. You only need direction of the close and total volume. The rest is a running sum.

How It Works

OBV updates one bar at a time using three cases:

If Close > Previous Close:  OBV = Previous OBV + Volume
If Close < Previous Close:  OBV = Previous OBV - Volume
If Close = Previous Close:  OBV = Previous OBV

The series starts from any chosen base, often zero or the first bar's volume. Because of that, only relative movement matters.

Traders read OBV in three ways. First, slope: a rising OBV with rising price supports the trend, while a falling OBV during a rally warns of weak participation. Second, breakouts: a fresh OBV high before price breaks resistance often precedes the breakout. Third, divergence: price and OBV moving opposite directions at swing extremes is the classic reversal warning.

Worked Example

Suppose OBV begins at zero. Over five bars:

• Bar 1, close up, volume 2.0M, OBV = +2.0M
• Bar 2, close up, volume 2.5M, OBV = +4.5M
• Bar 3, close down, volume 3.0M, OBV = +1.5M
• Bar 4, close down, volume 1.0M, OBV = +0.5M
• Bar 5, close up, volume 2.0M, OBV = +2.5M

Now imagine the stock pushes to a new five-week high a few bars later, but OBV does not exceed its prior peak of +4.5M. That is a textbook bearish divergence. Price says new strength; volume flow says supply pressed in on the way up.

Conversely, if price retests a recent low while OBV holds well above its corresponding trough, accumulation is showing through. The line gives you a way to see what is going on under the surface of the close.

Common Mistakes

1. Focusing on absolute OBV level. Because the starting point is arbitrary, comparing OBV across stocks or platforms is meaningless. Only the shape of the line carries information.
2. Equating all volume. OBV treats one share at the open auction the same as one share in a thin afternoon session. Realized order flow is much more granular.
3. Trading every OBV cross of a moving average. Choppy markets create false crosses. Pair OBV with price structure or a trend filter.
4. Ignoring flat closes. OBV is unchanged on flat closes, but on intraday charts the flat-close case is rare and traders sometimes treat near-flat closes as up or down inconsistently.
5. Skipping divergences. Granville built OBV largely as a divergence tool. Using it only as a trend follower wastes its most documented strength.

Frequently Asked Questions

What is OBV on balance volume in simple terms? OBV on balance volume is a running total of volume that goes up on days when price closes higher and down on days when price closes lower, used as a proxy for buying or selling pressure.

How does OBV on balance volume affect investment decisions? Investors use OBV to confirm or doubt price trends. A new price high backed by a new OBV high suggests strong participation, while a new price high without an OBV high warns of fading demand.

What is a real-world example of OBV on balance volume? On a daily SPY chart, OBV typically tracks price closely during sustained rallies. When a rally tops, OBV often stalls before price, and that flattening is the divergence Granville highlighted.

How can investors use OBV on balance volume effectively? Plot it under price, look for divergence at swing highs and lows, and overlay a moving average on the OBV line itself to filter noise. Do not trade absolute levels.

How is OBV on balance volume different from Price Volume Trend? OBV adds the entire bar's volume based on close direction. Price Volume Trend adds only a fraction of volume scaled by the percentage price change, so PVT reacts to size of move, not just sign.

Sources

1. StockCharts ChartSchool, On Balance Volume (OBV). https://chartschool.stockcharts.com/table-of-contents/technical-indicators-and-overlays/technical-indicators/on-balance-volume-obv
2. Granville, J. (1963). Granville's New Key to Stock Market Profits, Prentice-Hall. https://archive.org/details/granvillesnewkey0000gran
3. Incredible Charts, On Balance Volume (OBV). https://www.incrediblecharts.com/indicators/on_balance_volume.php
4. Corporate Finance Institute, On-Balance Volume Indicator (OBV). https://corporatefinanceinstitute.com/resources/career-map/sell-side/capital-markets/on-balance-volume-indicator-obv/

Disclaimer

This article is educational content only and is not financial advice. Nothing here is a recommendation to buy, sell, or hold any security. Consult a licensed advisor before making investment decisions.