What is on-balance volume (OBV)?
On-balance volume (OBV) is a running total of volume that adds a period's volume when price closes higher and subtracts it when price closes lower. The idea is that volume shows whether buyers or sellers are in control. A rising OBV line suggests buying pressure, a falling line suggests selling pressure, and divergences between OBV and price can warn that a move is losing support.
OBV was introduced by Joseph Granville in his 1963 book on stock market timing. It remains one of the simplest volume indicators and is built into almost every charting platform. This guide covers the formula, a worked calculation, the main signals and the limits you should know.
How OBV is calculated
OBV uses only the closing price and volume of each bar. Starting from any baseline, apply one of three rules:
- If today's close is higher than yesterday's close: OBV = previous OBV + today's volume.
- If today's close is lower than yesterday's close: OBV = previous OBV - today's volume.
- If today's close is unchanged: OBV = previous OBV.
Notice that the size of the price move does not matter. A day that closes one cent higher adds the full day's volume, just like a day that closes five dollars higher.
Worked example: calculating OBV
Here is a six-day calculation for a stock, starting OBV at zero on day 1.
| Day | Close | Volume | Change vs prior close | OBV |
|---|---|---|---|---|
| 1 | $50.00 | 10,000 | Start | 0 |
| 2 | $50.80 | 12,000 | Up, add 12,000 | 12,000 |
| 3 | $50.40 | 8,000 | Down, subtract 8,000 | 4,000 |
| 4 | $50.40 | 9,000 | Unchanged | 4,000 |
| 5 | $51.20 | 15,000 | Up, add 15,000 | 19,000 |
| 6 | $51.00 | 6,000 | Down, subtract 6,000 | 13,000 |
Over these six days, up days carried 27,000 shares of volume and down days carried 14,000. OBV finished at 13,000, the difference between the two. The two down days came on lighter volume than the up days, which is the kind of pattern OBV is designed to highlight.
The actual OBV number is not meaningful by itself, because it depends on where you start counting. What matters is the direction and slope of the line and how it compares with price.
How to read OBV
Trend confirmation
In a healthy uptrend, both price and OBV make higher highs. That shows volume is heavier on up days than down days. In a healthy downtrend, both make lower lows. When price and OBV move together, the trend has volume behind it.
Divergence
Divergence is the most watched OBV signal:
- Bearish divergence: price makes a higher high but OBV makes a lower high. The rally is happening on weaker volume.
- Bullish divergence: price makes a lower low but OBV makes a higher low. Selling volume is drying up.
Divergences can last a long time before price turns, and sometimes price never turns at all. Treat them as a warning to tighten risk or wait for confirmation, not as an automatic reversal signal.
OBV breakouts
Some traders draw trendlines or horizontal levels on the OBV line itself. If OBV breaks above its own resistance while price is still stuck below a level, it can hint that buying pressure is building ahead of a price breakout. Pair this with a clear price level, such as those covered in our support and resistance guide, and with the rules in our breakout trading strategy.
Example: using OBV to filter a breakout
A stock has been stuck below resistance at $52.00 for several weeks. During that time, price has made three roughly equal highs, but OBV has made three rising highs. Volume on the up days is outpacing volume on the down days even though price is going nowhere. When price finally closes above $52.00 and OBV makes a new high with it, the breakout has volume confirmation.
Compare that with a breakout where price closes above $52.00 but OBV is flat or falling. That move is happening without broad participation and has a higher chance of failing. Neither case guarantees a result, but OBV gives you an extra reason to take or skip the trade.
OBV vs other volume indicators
| Indicator | What it measures | Typical use |
|---|---|---|
| OBV | Cumulative volume signed by close direction | Trend confirmation and divergence |
| VWAP | Average price weighted by volume, usually reset daily | Intraday fair value and trade location |
| Volume bars | Raw volume per period | Spotting spikes and quiet periods |
For intraday work, many traders prefer VWAP because it resets each session and maps directly onto price. OBV is more common on daily and weekly charts. Some traders also combine OBV with a momentum tool such as MACD, looking for both to agree before acting.
Limitations of OBV
- All-or-nothing volume. The full bar's volume is added or subtracted based only on the close, so a bar that closes up by a tiny amount counts the same as a strong rally.
- Volume spikes distort it. One unusually large day, such as an earnings release or index rebalance, can shift the line for a long time.
- Forex volume is limited. Spot forex has no single central exchange, so platforms show tick volume from one broker's feed rather than total market volume. OBV on forex is a rougher estimate. Exchange-traded markets such as stocks and futures give OBV more reliable input.
- It lags in fast reversals. As a cumulative line, OBV can take time to reflect a sudden change in behavior.
OBV works best as a supporting tool alongside price structure and a clear plan. Browse our trading indicators library to compare it with other options.
Trading involves substantial risk of loss. Volume indicators such as OBV can give false or late signals and should not be used alone. This guide is educational only and is not financial advice. Read our full risk disclaimer.