OBV

On-Balance Volume (OBV) is a running total of volume that shows whether trading activity is backing a price move. This calculator rolls OBV forward by one session using Joseph Granville's original rule.

How the calculation works

Joseph Granville introduced OBV in his 1963 book on stock market timing. The rule is simple: if today's close is higher than yesterday's, the whole day's volume is added to OBV; if it is lower, the volume is subtracted; if the close is unchanged, OBV stays the same. Only the direction of the close matters, not the size of the move.

The inputs are Yesterday's OBV (the running total up to the previous session, which may be negative), Today's volume (shares, contracts or lots traded), Today's close and Yesterday's close. The currency of the price does not matter, because the calculator only compares the two closes.

Alongside the new OBV you see the day's OBV change and a short note telling you whether volume was added, subtracted or left out. That makes it easy to check a spreadsheet or charting platform, or to extend an OBV series by hand one bar at a time.

Worked example

Yesterday's OBV is 1,000,000. Today 250,000 shares traded and the stock closed at $105 versus $100 the day before. The close is higher, so volume is added: OBV = 1,000,000 + 250,000 = 1,250,000, a change of +250,000. Had it closed at $98, OBV would drop to 750,000; at exactly $100 it would stay at 1,000,000.

Things to keep in mind

• The absolute OBV number depends on the start date of the series and means nothing on its own. Read the slope and direction of the line.
• The classic signal is divergence: price makes a new high while OBV does not, or the other way round. Treat it as a prompt to look closer, not as a trade trigger.
• One-off volume spikes such as index rebalancing, option expiration or earnings days can shift OBV sharply and distort it for weeks.
• OBV ignores the size of the price change: a 0.1% gain adds as much volume as a 10% gain. The Chaikin Accumulation/Distribution line weights volume by where the close sits in the day's range.
• No indicator guarantees returns. Combine OBV with price analysis and position sizing.